Hyaluronic Sea Serum
Hyaluronic Sea Serum
Product Description
Product overview
OSEA's Hyaluronic Sea Serum is a high-performance, fast-absorbing hydrating serum clinically shown to improve skin elasticity and visibly reduce fine lines and wrinkles. Powered by dual-molecular-weight hyaluronic acid, Japanese Miru Seaweed (Codium Fragile), Snow Mushroom, and a volcanic marine ferment, this fragrance-free formula delivers instant and lasting hydration for all skin types — without a single synthetic, paraben, or phthalate.
Dual Molecular Weight HA
High molecular weight sodium hyaluronate creates a moisture-locking barrier at the surface, while hydrolyzed hyaluronic acid penetrates deeper skin layers for multi-level hydration.
Texture & feel
SENSORYDual Molecular Weight HA
High molecular weight sodium hyaluronate creates a moisture-locking barrier at the surface, while hydrolyzed hyaluronic acid penetrates deeper skin layers for multi-level hydration.
Japanese Miru Seaweed (Codium Fragile)
This rare green sea algae is naturally rich in hyaluronic acid and minerals, replenishing and balancing the skin's moisture levels for a healthy, hydrated complexion.
Snow Mushroom (Tremella Fuciformis)
Called the "beauty mushroom" in Traditional Chinese Medicine, Tremella forms a hydration film on the skin surface — similar to hyaluronic acid but with superior water-retention properties.
Volcanic Marine Ferment (Bacillus Ferment)
This unique ferment derived from volcanic marine microorganisms effectively plumps and smooths the appearance of fine lines, supporting a visibly firmer-looking complexion.
Honeysuckle Flower Preservative System
Instead of synthetic preservatives, OSEA uses Lonicera Japonica and Lonicera Caprifolium honeysuckle flower extracts — natural antimicrobials that keep the formula fresh and safe.
Clinically Proven Results
Clinically shown to deliver instant hydration, strengthen the moisture barrier, improve skin elasticity, and reduce the appearance of fine lines, crow's feet, laugh lines, and frown lines.
Safety & compatibility
SAFEContains no retinoids, salicylic acid, hydroquinone, or chemical UV filters. The formula is free from synthetic fragrances and harsh actives. Considered safe during pregnancy and breastfeeding — always confirm with your OB/GYN or dermatologist.
Contains Bacillus Ferment, a fermented ingredient that may potentially feed Malassezia yeast. Those with active fungal acne should patch test or choose an alternative. The rest of the formula is FA-friendly.
Oil-free, silicone-free formula with only low-comedogenic ingredients. Suitable for acne-prone and oily skin types. No pore-clogging oils or waxes in the formula.
Fragrance-free, dye-free, paraben-free, and sulfate-free. Dermatologist tested. Formulated without known common irritants. Patch test recommended for very reactive or rosacea-prone skin.
Hyaluronic acid is a universal booster and layering partner. Apply this serum before retinol or vitamin C to cushion skin and reduce irritation. Do not mix directly with high-strength acids in the same application step.
PETA certified vegan and cruelty-free. No animal-derived ingredients. Leaping Bunny aligned brand practices. Sustainable glass packaging to minimize environmental impact.
Ingredient breakdown
INGREDIENTSWater (Aqua/Eau) ~60%+Base
The primary solvent and base of the formula. Pharmaceutical-grade purified water ensures optimal delivery of all active ingredients and provides the serum's light, watery consistency.
- Function: Solvent, hydration delivery base
- Safety: Universally safe for all skin types
Codium Fragile Extract (Japanese Miru Seaweed) ~5–10%Proven
The hero marine ingredient in OSEA's lineup. Codium Fragile is a nutrient-dense green seaweed naturally rich in its own hyaluronic acid, sulfated polysaccharides, vitamins, and minerals. It actively replenishes and balances the skin's moisture levels, delivering antioxidant protection alongside deep hydration.
- Key benefit: Natural source of HA-like polysaccharides that bind moisture to the skin
- Antioxidant capacity: Rich in vitamins A, C, E and carotenoids
- Study support: Marine algae extracts shown to support skin barrier function and reduce transepidermal water loss (TEWL)
Betaine ~2–5%Proven
A natural osmolyte derived from sugar beets. Betaine is a powerful humectant that draws moisture into the skin while also functioning as a skin-conditioning agent that softens and smooths texture. It also helps stabilize the formula's pH.
- Function: Humectant, skin conditioning, osmoprotectant
- Tolerance: Well tolerated by sensitive and rosacea-prone skin
- Synergy: Works alongside HA to enhance moisture retention
Sodium Hyaluronate (High Molecular Weight HA) ~1–2%Proven
The gold standard humectant in skincare. High molecular weight sodium hyaluronate sits on the surface of the skin, forming a flexible moisture-locking film that provides an immediate plumping and smoothing effect while preventing moisture evaporation.
- Mechanism: Holds up to 1,000x its weight in water
- Effect: Immediate surface plumping; reduces appearance of fine lines
- Clinical evidence: Extensively documented in peer-reviewed literature for improving skin hydration and elasticity
Tremella Fuciformis Sporocarp Extract (Snow Mushroom) ~1–3%Proven
Known as the "beauty mushroom" or snow fungus, Tremella Fuciformis has been used in traditional East Asian skincare for centuries. Its polysaccharides are structurally similar to hyaluronic acid but are smaller in particle size, allowing them to penetrate more deeply and hold moisture even more effectively than conventional HA.
- Water retention: Studies show polysaccharides hold up to 500x their weight in water
- Penetration: Smaller particle size vs. standard HA = deeper absorption
- Antioxidant: Contains natural antioxidants that protect against oxidative stress
Bacillus Ferment (Volcanic Marine Ferment) ~0.5–2%Promising
A fermented ingredient derived from volcanic marine microorganisms. This unique ferment contains bioavailable compounds that help smooth the appearance of fine lines, support skin renewal, and improve overall skin texture. The fermentation process enhances ingredient bioavailability and efficacy.
- Function: Skin-smoothing, anti-aging, texture-improving ferment
- Bioavailability: Fermentation process pre-digests molecules for better skin uptake
Hydrolyzed Hyaluronic Acid (Low Molecular Weight HA) ~0.5–1%Proven
The complementary counterpart to sodium hyaluronate. Hydrolyzed (broken down) hyaluronic acid has a smaller molecular weight that allows it to penetrate below the surface of the skin, delivering deep-layer moisture and supporting long-term plumping effects. Together, both HA forms provide complete multi-depth hydration.
- Penetration depth: Reaches deeper skin layers vs. high MW HA
- Long-term benefit: Supports collagen production environment and skin elasticity
- Clinical data: Dual-weight HA formulas shown to outperform single-weight in long-term moisture studies
Glycerin ~1–3%Proven
One of the most well-researched humectants in skincare. Glycerin draws water from the environment and deeper skin layers to the surface, keeping skin hydrated throughout the day. It also supports the skin barrier and improves the texture and spreadability of the formula.
- Function: Humectant, skin conditioner, barrier support
- Evidence base: Decades of clinical research confirming moisturizing efficacy
Lonicera Japonica & Lonicera Caprifolium Flower Extracts (Honeysuckle) ~0.5–1%Proven
These two honeysuckle flower extracts serve as the natural preservative system in this formula, replacing synthetic parabens and formaldehyde-releasing preservatives. They contain natural antimicrobial compounds (primarily chlorogenic acid) that protect product integrity. They also provide mild antioxidant and soothing benefits.
- Function: Natural preservative, antimicrobial, antioxidant
- Clean beauty alignment: Replaces synthetic parabens, phenoxyethanol alternatives
Sodium Copper Chlorophyllin (Copper Chlorophyll) tracePromising
A water-soluble derivative of chlorophyll, the green pigment found in plants. It provides potent antioxidant protection against environmental stressors and free radicals. Research suggests it may also have wound-healing, anti-inflammatory, and skin-brightening properties, making it a valuable secondary active in this formula.
- Function: Antioxidant, anti-inflammatory, skin-brightening
- Research: Studies indicate wound-healing and collagen-synthesis support properties
14 ingredients — Water / Aqua / Eau, Codium Fragile Extract, Betaine, Sodium Hyaluronate, Tremella Fuciformis Sporocarp Extract, Bacillus Ferment, Hydrolyzed Hyaluronic Acid, Glycerin, Sodium Benzoate, Potassium Sorbate, Citric Acid, Lonicera Japonica (Honeysuckle) Flower Extract, Lonicera Caprifolium (Honeysuckle) Flower Extract, Sodium Copper Chlorophyllin.
Ingredient lists may change over time. Please refer to the packaging for the most current INCI list.
Where it fits in your routine
ROUTINEPro Tip: Apply to slightly damp skin after misting with a hydrating toner (like OSEA Sea Minerals Mist) for amplified hydration. Always seal in with a moisturizer on top. Use morning and night.
How to use
HOW TO USECleanse
Start with a clean face. Use a gentle cleanser suited to your skin type, then pat dry — leaving skin slightly damp for best results.
Prep (Optional but Recommended)
Mist your face with a hydrating toner or facial mist. Applying the serum to damp skin helps humectants draw more moisture into the skin — enhancing the formula's effect.
Apply Serum
Dispense 2–3 drops from the dropper onto your fingertips. Press and gently pat the serum across your face and neck. Avoid rubbing — pressing allows better absorption.
Allow to Absorb
Let the serum fully absorb for 30–60 seconds before proceeding. You'll notice the skin feeling instantly plump and refreshed.
Seal with Moisturizer
Always follow with a moisturizer to lock in the hydration delivered by the serum. This step is critical — HA serums require an occlusive layer to prevent moisture from evaporating in dry environments.
AM Routine: Finish with SPF
In the morning, finish your routine with a broad-spectrum SPF 30+ sunscreen. The serum's antioxidant ingredients complement UV protection without interfering with sunscreen efficacy.
Who is it for?
WHOPerfect for you if:
- You want clinically proven hydration with clean, natural ingredients
- Your skin is dry, dehydrated, or losing plumpness with age
- You're looking for an oil-free, non-comedogenic formula for oily or combination skin
- You prefer fragrance-free formulas due to sensitivity
- You're pregnant or breastfeeding and want a safe serum
- You value sustainable, clean-beauty brand practices
- You want to reduce the appearance of fine lines without retinol
Consider alternatives if:
- You have active fungal acne (Malassezia folliculitis) — Bacillus Ferment may not be suitable
- You're on an extremely tight budget (there are cheaper HA serums available)
- You need a heavy-duty treatment serum for deep wrinkles or severe hyperpigmentation
- You prefer a larger bottle size for the price point
- You need a serum with added actives like niacinamide, vitamin C, or retinol
Skin type compatibility
SKIN TYPESDual-weight HA plus Snow Mushroom and seaweed deliver deep, lasting moisture. Layers beautifully under richer creams for intense hydration relief.
Completely oil-free and silicone-free. Fast-absorbing watery texture leaves no greasiness or shine — even under makeup. Won't clog pores.
Balances hydration across T-zone and drier cheek areas without over-moisturizing oily zones. One of the best skin types for this formula.
Fragrance-free, dye-free, and dermatologist tested. Gentle enough for most sensitive skin. Patch test recommended for rosacea-prone or highly reactive skin.
Non-comedogenic and oil-free. Provides hydration without triggering breakouts. Note: Bacillus Ferment may be a concern for fungal acne sufferers specifically.
Clinically proven to improve skin elasticity and visibly reduce fine lines and wrinkles. The combination of dual HA and marine actives is ideal for aging, volume-depleted skin.
Results timeline
MONTH 2–3Instant Plumping & Hydration Boost
Skin feels noticeably more hydrated, plump, and supple within minutes of first application. Surface fine lines appear temporarily smoothed due to moisture-binding action of HA.
~90% noticed immediate hydrationImproved Skin Texture & Softness
Consistent twice-daily use starts visibly improving skin texture. Skin feels softer, looks more even, and foundation applies more smoothly. Dryness and tightness significantly reduced.
~75% noticed improved softnessVisible Fine Line Reduction
Shallow fine lines and early wrinkles begin to visibly soften as the dual-depth HA supports ongoing hydration from within. Skin looks more refreshed and youthful at rest.
~65% noticed fine line improvementImproved Elasticity & Firmness
Clinically documented elasticity improvements become more apparent. The volcanic marine ferment and seaweed complex support skin resilience. Deeper wrinkles appear softened; skin looks lifted and firmer.
~55% noticed elasticity improvementRatings by platform
3K+ REVIEWSPros & cons
BALANCEDPraised
- Clinically proven hydration, elasticity improvement, and fine line reduction
- Dual molecular weight HA for multi-depth moisture delivery
- 100% fragrance-free — suitable for even sensitive noses
- Clean, short ingredient list (14 ingredients total)
- Fast-absorbing — no greasy or sticky residue
- Beautiful frosted glass bottle with precise dropper
- Works morning and night for all skin types
- Pregnancy-safe and vegan formula
- Unique marine and botanical actives not found in drugstore alternatives
Criticized
- Premium price point ($88 for 1 fl oz / 30ml)
- Bottle lasts only 6–8 weeks with twice-daily use
- Not ideal for those with active fungal acne due to Bacillus Ferment
- Subtle earthy/oceanic scent from natural ingredients (though listed fragrance-free)
- May feel slightly tacky in very humid or dry environments
- Results for anti-aging effects require consistent 4–8 week use
- No additional active ingredients (e.g. no niacinamide, peptides, vitamin C)
Budget-friendly alternatives (dupes)
DUPESA simple, effective HA serum with 3 molecular weights of hyaluronic acid and vitamin B5. Lacks the unique marine complex and Snow Mushroom of OSEA but delivers strong surface and mid-depth hydration at a fraction of the cost. Fragrance-free and vegan. Best for budget-conscious hydration seekers.
A widely available drugstore option with hyaluronic acid and glycerin. Contains sodium hyaluronate crosspolymer for longer-lasting moisture. Lacks the marine bioactives, Snow Mushroom, and natural preservative system. Contains synthetic ingredients that OSEA avoids. Good entry-level HA serum for value shoppers.
A clean-beauty alternative with sodium hyaluronate, pro-vitamin B5, pineapple ceramide, and fruit extracts. Comparable clean credentials and texture. Lacks seaweed complex and Snow Mushroom. Both are fragrance-free with a focus on hydration. Slightly more affordable with a larger 50ml size for the price.
Comparison with competitors
SIDE-BY-SIDEStorage & shelf life
12 MONTHS12 months after opening. Check the bottom of the bottle for the PAO symbol (open jar icon with "12M").
Store in a cool, dry place away from direct sunlight and heat. Avoid storing in humid bathroom environments. Room temperature (15–25°C / 59–77°F) is ideal.
Frosted glass bottle with glass dropper dispenser. Sustainable packaging — the glass bottle is recyclable. OSEA co-founded the nonprofit Pact for beauty packaging recycling.
Yes — at 30ml (1 fl oz) this is under the 100ml TSA/airline carry-on liquid limit. The glass dropper bottle is secure but fragile; consider a protective case for travel.
Frequently asked questions
FAQYes, the OSEA Hyaluronic Sea Serum is generally considered safe for use during pregnancy and breastfeeding. The formula contains no retinoids (vitamin A derivatives), salicylic acid, hydroquinone, chemical UV filters, or synthetic fragrances — the primary ingredients flagged as concerns during pregnancy. The active ingredients (hyaluronic acid, seaweed extracts, Snow Mushroom, glycerin, betaine) are all well-tolerated and widely considered safe. As with any skincare product used during pregnancy, we recommend consulting your OB/GYN or dermatologist before use.
Mostly yes, but with one caution: the formula contains Bacillus Ferment, a fermented ingredient. Fermented ingredients can in some cases feed Malassezia yeast, the fungus responsible for fungal acne (also called pityrosporum folliculitis). The rest of the formula — water, sodium hyaluronate, hydrolyzed hyaluronic acid, glycerin, betaine, seaweed extracts, Snow Mushroom — is considered fungal-acne safe. If you have active fungal acne, we recommend patch testing the serum first or consulting your dermatologist before incorporating it into your routine.
Yes — hyaluronic acid is one of the most universally compatible skincare ingredients. With retinol: apply the serum first (on damp skin), allow it to absorb, then apply your retinol product on top — the HA cushions skin and reduces retinol-associated dryness and irritation. With vitamin C: apply the Hyaluronic Sea Serum before your vitamin C serum as a hydration base. With AHAs/BHAs: the serum can be used as a post-exfoliant step to replenish moisture, or applied before actives as a base layer. Avoid mixing multiple actives in the same step — apply in layers and allow each to absorb.
OSEA Hyaluronic Sea Serum is formulated for all skin types. It is particularly excellent for dry, dehydrated, combination, and mature skin due to its multi-depth hydration approach. Oily skin types also respond well because the formula is oil-free and non-comedogenic — it provides hydration without adding shine. Sensitive skin generally tolerates the formula well since it is 100% fragrance-free and dermatologist-tested. The formula is OSEA's best-seller precisely because it works across all skin types and concerns.
You will notice immediate plumping and hydration benefits within minutes of the first application — this is the hyaluronic acid at work. For visible fine line softening, most users report improvement within 2–4 weeks of consistent twice-daily use. For clinically documented improvements in skin elasticity and deeper wrinkle reduction, plan for a consistent routine of 4–8 weeks minimum. Results vary based on skin type, baseline hydration levels, environment (humidity), and whether a moisturizer is applied on top to lock in the serum's benefits.
Apply the Hyaluronic Sea Serum as Step 3 in your routine: after cleansing and any toner or mist, and before your treatment serum, moisturizer, and SPF. The general rule is thinnest-to-thickest. As a water-based serum, it goes on before heavier treatments and creams. Pro tip from OSEA: apply to slightly damp skin — mist your face first with a hydrating toner or facial mist, then apply the serum immediately. Humectants like HA work best when there is moisture available to attract into the skin. Always seal with a moisturizer to prevent moisture evaporation.
No — the OSEA Hyaluronic Sea Serum is non-comedogenic with a comedogenic rating of 1 out of 5. The formula is 100% oil-free and silicone-free. It contains no known pore-clogging ingredients such as oils, waxes, or heavy emollients. All key actives — hyaluronic acid, glycerin, betaine, seaweed extract, Snow Mushroom — have low-to-zero comedogenic ratings. This makes it an excellent choice for acne-prone, oily, and congestion-prone skin types who need hydration without the risk of breakouts.
The Period After Opening (PAO) for OSEA Hyaluronic Sea Serum is 12 months — you'll find this indicated by the open-jar symbol on the packaging. In terms of how long one bottle lasts in daily use: with 2–3 drops per application, used twice daily (morning and night), one 30ml (1 fl oz) bottle typically lasts approximately 6–8 weeks. For best results and product integrity, store in a cool, dry place away from direct sunlight and heat, and avoid leaving the dropper open for extended periods.
Verdict: The OSEA Hyaluronic Sea Serum is a standout clean beauty hydrator that punches above its weight with a uniquely marine-powered formula. What sets it apart from generic HA serums is its proprietary combination of Japanese Miru Seaweed (Codium Fragile), dual molecular-weight hyaluronic acid, Snow Mushroom, and a volcanic marine ferment — delivering clinically proven hydration, elasticity improvement, and fine line reduction in just 14 clean ingredients. It is 100% fragrance-free, pregnancy-safe, oil-free, and suitable for all skin types. The premium $88 price point and small 30ml bottle size are the primary limitations, but for those who prioritize clean, efficacious, marine-powered skincare with sustainability credentials, this serum earns its cult-favorite status. Highly recommended for anyone seeking a serious hydration upgrade without compromising on ingredient quality.
Product Overview
Quick product notes are a great way to check if a product is free from commonly avoided ingredients by skincare enthusiasts. These preferences come about for different reasons depending on the ingredient such as personal experiences, sensitivities, health preferences & etc.
Just because a product is not free from a common preference does not mean it's a bad product! You can make a personal decision whether or not you want to use a product that contains these ingredients or not - click the labels of the preference to read more about them.
Quick Product Notes
Ever used a product that promised a certain effect but provided no results? It might not have contained any notable ingredients that could have been responsible for that promised effect. It doesn't matter what the marketing or packaging «promises» it can do, if it doesn't contain anything that can help - then the likelihood of it helping is low.
We help you identify key notable ingredients that have been shown to help with effects such as acne-fighting, brightening, UV-protection, wound healing & anti-aging to help you achieve your skincare goals smarter. Please note that different notable ingredients have varying levels of research behind them, some are extremely well proven yet some have mixed research in their efficacy.
Just because a product doesn't contain any notable ingredients doesn't mean it's bad. And a product with notable ingredients (or even many) doesn't necessarily guarantee the efficacy of the product performing these effects either. There are other factors such as ingredient quality, concentration and formulation that will ultimately determine this.
Be smart and use this as just a starting point for you to make more informed and smarter choices and compare it with reviews to see if the product is right for you
Notable Effects & Ingredients
Why are some products great for some people and horrible for others? Well everyone has different skin types and different reactions to the same ingredients.
We've identified a range of ingredients that are commonly regarded as potentially good or bad for those with Dry, Oily/Acne-Prone or Sensitive skin.
A product that contains good or bad ingredients for your skin type doesn't always flat out make the entire product good or bad for your skin. There are other factors such as ingredient quality, concentration and formulation that will ultimately determine your skins reaction.
One of the best ways to use this section is to troubleshoot products you've had bad experiences with in the past. Check if it contains any of the marked ingredients to point out suspect ingredients to avoid in the future!
Ingredients Related to Skin Types
Ingredient Safety Breakdown refers to the percentage % of ingredients in different risk categories as classified by EWG (Environment Working Group) if they are available. There are almost endless cosmetic ingredients and they are one of the few organisations globally that have assigned ratings to a lot of the more commonly used ingredients which is why we reference them.
EWG is seen by many to be more on the alarmist side in their assignment of health ratings resulting in rating ingredients as riskier than they actually are. We recommend using this a reference point rather than a strict guide of ingredient safety and to always do further research if into ingredients that you may find suspect.
Ingredient Safety Breakdown
Product ingredient list
| EWG | CIR | Ingredient Name & Cosmetic Functions | Notes |
|---|---|---|---|
| 0 |
Codium Fragile Extract
Skin Conditioning
|
|
|
| 1 |
Betaine
Skin Conditioning, Humectant, Viscosity Controlling, Antistatic Agent, Hair Conditioning
|
Hydrating
Irritation
Dark Spots
|
|
| 0 |
Tremella Fuciformis Sporocarp Extract
|
|
|
| 1 |
Bacillus Ferment
Skin Conditioning
|
|
|
| 0 |
Hydrolyzed Hyaluronic Acid
Humectant, Skin Conditioning
|
Promotes Wound Healing
Hydrating
|








