Biodegradable swimwear is often marketed as a sustainable alternative to conventional nylon or polyester suits. However, the term biodegradable is frequently misunderstood or misused. Many products labelled “eco-friendly” still rely on synthetic polymers, recycled plastics, or materials that do not biodegrade under real-world environmental conditions.
This guide separates facts from marketing claims, explains the science of textile biodegradation, and helps you evaluate materials, certifications, and environmental impacts based on established standards.
Key Takeaways
Biodegradable ≠ falls apart in water. Biodegradation requires specific environmental conditions—microbes, moisture, heat—and does not occur during normal wear.
OEKO-TEX does not certify biodegradability. It certifies the absence of harmful substances, not whether a fibre degrades.
Recycled ≠ biodegradable. Fabrics like ECONYL® reduce waste but do not decompose into natural elements.
Biodegradation timelines depend on conditions. Claims such as “degrades in 5 years in landfill” only apply to controlled test environments, not all landfills.
Natural fibres degrade faster, but are not always swimwear-appropriate. Cotton, hemp, and wool can biodegrade, yet they lack chlorine and salt-water performance.
Certifications matter. Look for recognised standards (e.g., GOTS, Fair Trade, OEKO-TEX, ASTM/ISO biodegradation testing) and transparent material information.
1. What Makes a Swimwear Material “Biodegradable”?
To qualify as biodegradable, a textile must break down into natural elements (such as CO2, water, biomass or, under anaerobic conditions, methane) through microbial activity. This is typically assessed under controlled laboratory environments using standards such as:
ASTM D6400 – compostable plastics (industrial composting)
ASTM D6691 – degradation of plastics in a marine environment
ISO 20136 – degradation of cellulose textile products
ISO 14855 – controlled aerobic biodegradation of plastics under composting conditions
Conditions Required for Biodegradation
Biodegradation occurs only when the material is exposed to the right combination of:
Microorganisms (bacteria, fungi, etc.)
Temperature within the range required for microbial activity
Moisture at appropriate levels
Oxygen conditions (aerobic or anaerobic), depending on the polymer and test method
These conditions are not present in oceans or during normal swimming activities, which means biodegradable polymers maintain performance during wear and do not “dissolve” in water.
2. Common Misconceptions About Sustainable Swimwear
Myth 1: Biodegradable Swimwear Breaks Down in the Water
Biodegradable swimwear is designed to perform like conventional swimwear during use. Laboratory studies on textile degradation show that:
Natural cellulose-based fibres (such as cotton) can degrade relatively quickly under marine test conditions.
Bio-based plastics and biopolymer blends often show minimal degradation over many months in similar tests.
Swimwear-grade biodegradable synthetic fibres are engineered for resistance to water, UV, chlorine, and abrasion, just like traditional nylon. You can swim, sunbathe, and wash these garments without them breaking down in use.
Myth 2: OEKO-TEX Means “Biodegradable”
OEKO-TEX® certifications (such as Standard 100 or MADE IN GREEN) focus on:
Chemical safety (limits on harmful substances)
Human ecological safety (skin contact safety)
Responsible and traceable manufacturing in some schemes
They do not indicate whether a fabric is biodegradable or compostable. Any statement that equates “OEKO-TEX certified” with “biodegradable” should be corrected.
Myth 3: “Eco-Friendly” or “Recycled” Means Biodegradable
Many brands describe their products as “eco-friendly” because they use:
Recycled polyester
ECONYL® regenerated nylon
Recycled PET (rPET)
These materials help reduce dependence on virgin fossil resources and can lower overall environmental impact, but they do not biodegrade. They are still synthetic polymers and can persist in the environment for a long time.
Biodegradable is a separate property that applies only when a material can break down via microbial activity into natural substances under specified conditions.
Myth 4: “Breaks Down in 1–5 Years in Landfill” Applies Everywhere
Claims such as “this fabric biodegrades in 5 years in landfill” typically refer to accelerated anaerobic digestion tests performed under tightly controlled laboratory conditions, where temperature, moisture, and microbial activity are optimised.
Real-world landfills vary greatly in:
Oxygen availability
Moisture levels
Temperature
Compaction and waste composition
As a result, actual degradation times can be significantly longer, and not all items labelled as “biodegradable” will fully break down in every landfill. Any timeline should always be presented with the caveat that it is based on specific test conditions.
3. Materials Used in “Biodegradable” Swimwear
A. Plant-Based Fibres (Not Typically Used for Performance Swimwear)
Plant-based fibres include cotton, hemp, bamboo, and linen. These fibres are derived from renewable resources and can biodegrade under aerobic conditions.
Advantages:
High biodegradability when conditions are suitable
Renewable origin
Do not create persistent microplastics
Limitations for Swimwear:
High water absorption
Limited chlorine and UV resistance
Reduced elasticity and recovery when wet
Heavier feel and slower drying times
These fibres can be excellent for beach cover-ups, resort wear, or UV shirts, but they are generally not suitable as the main fibre for high-performance swimwear that needs durable stretch and shape retention.
B. Biopolymers & Enhanced-Biodegradation Polyamides
Several swimwear brands use specialised polymers or elastomeric fibres designed for enhanced biodegradation in specific environments. Examples include:
Enhanced-biodegradation polyamides (e.g., certain polyamide 6.6 formulations)
Biodegradable stretch yarns tested using ASTM or ISO biodegradation methods
Bio-based elastomers made partly from renewable feedstocks (such as castor oil–based polyamides)
Advantages:
Provide stretch, recovery, and fit similar to conventional nylon/spandex
Engineered to degrade more quickly than standard synthetics under specific conditions
Allow the construction of performance swimwear with improved end-of-life prospects
Limitations:
Require specific conditions (often anaerobic) to biodegrade
Do not necessarily degrade in oceans or surface waters
Can still shed microfibres, although persistence may be lower than conventional synthetics
4. Environmental Comparisons
A. Environmental Impact Overview
Material Type | Biodegradation Potential | Microplastic Persistence | Key Notes |
|---|---|---|---|
Conventional Nylon/Polyester | Very low | High | Can persist for decades or longer in the environment |
Recycled Synthetics (e.g., ECONYL®, rPET) | Low | High | Lower raw material footprint but still non-biodegradable |
Enhanced-Biodegradation Polyamides | Moderate (in specific anaerobic or controlled conditions) | Potentially reduced persistence | Performance similar to conventional synthetics |
Natural Fibres | High (under aerobic conditions) | None | More suitable for casual beachwear than performance swimwear |
B. Durability and Performance
Biodegradable or enhanced-biodegradation synthetic fibres are engineered to offer:
Good stretch and recovery
Colourfastness
Resistance to chlorine and salt water
Comfort and fit comparable to traditional swimwear fabrics
As with all swimwear, actual durability depends on fabric quality, garment construction, and care routines.
C. Skin Sensitivity Considerations
For people with sensitive skin or conditions like eczema, fabric choice and chemical finishes can make a noticeable difference. Some consumers report better comfort with:
OEKO-TEX® Standard 100 certified fabrics
Garments using less aggressive dyes and reduced chemical finishes
Natural fibre garments for beachwear and cover-ups (even if not used in swimwear itself)
5. How to Choose Truly Biodegradable Swimwear
A. Read Material Labels Carefully
When you examine a swimwear label, look for clear, specific information rather than vague marketing language. Useful details might include:
Exact fibre composition (e.g., “polyamide with enhanced biodegradation” and elastane percentage)
Names of branded biodegradable fibres where applicable
Any mention of ASTM or ISO biodegradation tests and conditions
Be cautious of labels that only use terms such as “eco-friendly,” “green,” or “sustainable” without explaining how the product is more sustainable.
B. Verify Certifications and Evidence
Look for recognised third-party certifications, and understand what each one covers:
Material Safety & Chemical Transparency
OEKO-TEX® Standard 100 – tests finished products for harmful substances.
OEKO-TEX® MADE IN GREEN – combines product safety with responsible, traceable production.
Organic and Ethical Production
GOTS (Global Organic Textile Standard) – covers organic fibre content and environmental and social criteria.
Fair Trade Certified – focuses on fair labour practices and community support.
Biodegradation Testing (Methods, Not “Logos”)
Biodegradability is validated through test reports rather than a single universal label. Brands may reference:
ASTM D5511 (anaerobic biodegradation under high-solids conditions)
ASTM D5338 (composting conditions)
ISO 14855 (aerobic biodegradation)
ISO 20136 (degradation of cellulose-based materials)
When possible, check whether the brand discloses the test method, conditions, and degradation percentage achieved during the test period.
C. Questions to Ask Before You Buy
What fibres are used, and what is the exact composition of the fabric?
Has the material been tested for biodegradation using ASTM or ISO standards?
Under what conditions (temperature, oxygen, environment) does biodegradation occur?
Which chemical safety or sustainability certifications does the fabric or product carry?
Does the brand provide guidance on washing to minimise microfibre release?
6. FAQ
What does “biodegradable” mean in swimwear?
In the context of swimwear, “biodegradable” means that the fibre can be broken down by microorganisms into natural substances such as CO2, water, and biomass under specified conditions. This process does not occur during normal use in pools, oceans, or washing machines.
Does biodegradable swimwear break down in seawater?
No. The biodegradable or enhanced-biodegradation polymers used in swimwear are engineered to remain stable in water, including seawater. They generally require controlled conditions (such as those found in industrial composting or specific landfill test environments) to biodegrade.
How long does biodegradable swimwear take to break down?
Timelines vary widely and depend on the material and environment. Under controlled test conditions, biodegradation may occur within months to a few years. In real-world landfills or other environments, the process can take much longer and is less predictable. Always interpret “X years” claims as referring to test conditions only.
Is biodegradable swimwear safer for sensitive skin?
Biodegradability itself does not guarantee skin safety. For sensitive skin, look for:
OEKO-TEX® Standard 100 certification
Brands that disclose dye types and finishing processes
Simpler constructions with fewer harsh finishes
How can I tell if swimwear is truly biodegradable?
Genuine biodegradable swimwear should be supported by:
Clear fibre descriptions (not just “eco” or “green”)
References to recognised biodegradation test methods (ASTM/ISO)
Transparent communication about the environments in which biodegradation occurs
Summary: Biodegradable swimwear does not fall apart while you wear it. Instead, it is based on materials that can break down under specific controlled conditions. By understanding labels, certifications, and scientific terminology, you can make more informed and responsible choices when shopping for sustainable swimwear.