The Short Answer: Skip the Underwear (Here's Why)

Before we dive deep into the nitty-gritty, let's get one thing crystal clear: swim shorts are designed to be worn solo. Period. End of story. But we know some of you need more convincing than that, so let's talk facts.

Most quality swim shorts – like the ones we design here at shinesty.com – come with built-in mesh liners that do exactly what underwear is supposed to do: provide support and keep everything where it should be. Adding underwear on top of that is like wearing two condoms – counterproductive and awkward as hell.

6 Science-Backed Reasons to Ditch the Double Layer

1. Your Swimming Performance Takes a Hit

Let's talk hydrodynamics, because yes, this actually matters even if you're not training for the Olympics. Underwear absorbs water like a sponge, creating drag that makes you slower and less efficient in the water. Research shows that wearing underwear while swimming can increase hydrodynamic drag by up to 40% compared to proper swimwear.

Think about it – competitive swimmers wear skin-tight suits designed to reduce water drag. Modern competitive swimwear uses special low resistance fabrics that reduce skin drag. Meanwhile, you're out here adding an extra layer that's basically a water-collecting parachute.

2. Chemical Warfare on Your Favorite Underwear

Pool chemicals and saltwater are brutal on fabric, especially the soft, comfortable materials used in quality underwear. Chlorine breaks down fibers and fades colors faster than you can say "cannonball." The chlorine slowly eats away at the fibres, making them thinner and thinner. Eventually, the threads become so small and weak they tear under regular use. Thread degradation due to chlorinated water is worse in natural fibres like cotton.

Save your good underwear for dry land activities where it can do what it does best – keep you comfortable all day with moisture-wicking, breathable performance.

3. Bacterial Playground Alert

Here's where things get gross (but important). Wet underwear creates the perfect environment for bacteria to throw a party, and trust us, you don't want to be the venue. "Yeast and bacteria really thrive in moist, dark places, like a wet bathing suit or wet workout clothes," according to medical experts. The inside of a wet swimsuit is both warm and moist, so it's basically a breeding ground for bacteria.

Studies indicate that prolonged exposure to wet clothing increases bacterial growth rates significantly, particularly in warm, humid environments. When you are out enjoying summer fun at the beach, you're going to be having increased moisture in your bathing suit, and that sets up a nice wet warm environment for bacteria. Anderson says bacteria can form in a matter of minutes.

4. Chafing City, Population: You

Double layers plus water plus movement equals friction, and friction equals chafing. Even if your underwear normally prevents chafing (like our anti-bunching, no-itch stitching designs), adding water to the equation changes everything. Wet fabric behaves differently, bunching and rubbing in ways that'll leave you walking funny for days.

5. Pool Filter Sabotage

This one's for the greater good – cotton fibers from underwear break down in chlorinated water and can clog pool filtration systems. When the fibers spend enough time in the water, they can begin breaking down and separating from your garment. If enough fibers travel in a cluster, they can get into your pool's filter and back it up. When this happens, they have to be processed by the pool filter; if you and other people are wearing underwear in the pool regularly, then this could destroy the pool's filter. Don't be that guy who ruins the pool for everyone else.

6. Fashion Police Citation

Let's be real about the visual situation here. Wet underwear creates visible lines, bunching, and that telltale waistband peek that screams "I don't know what I'm doing." It's the aquatic equivalent of socks with sandals – a dead giveaway that you missed the memo on proper swimwear etiquette.

Understanding Swim Short Design: Built-in Protection

Quality swim shorts aren't just regular shorts that happen to get wet – they're engineered for water activities. Most feature:

• Mesh liners that provide support and prevent awkward situations
• Quick-dry fabrics that shed water efficiently
• Proper fit that stays put without additional layers
• Strategic construction for comfort and performance

When you shop our collection at shinesty.com, you're getting swim shorts that have done the heavy lifting for you – no additional underwear required.

The Rare Exceptions: When Rules Get Bent

Okay, we're reasonable people here at Shinesty, so let's acknowledge the few scenarios where you might consider breaking the no-underwear rule:

Beach Day, No Swimming

If you're wearing swim shorts purely for the aesthetic but have zero intention of getting wet, then sure, underwear won't hurt. Think beach volleyball tournaments or poolside grilling where you're staying dry.

Swim Shorts Without Liners

Some board shorts skip the built-in liner entirely. In these cases, you might want some kind of support – though we'd recommend compression shorts specifically designed for water activities rather than regular underwear.

Medical Considerations

If you have specific medical conditions that require extra protection or support, consult with your doctor about the best approach. Your health trumps swimming etiquette every time.

What to Do If You're Uncomfortable Going Commando

We get it – some guys have been wearing underwear under swim shorts their whole lives, and change feels weird. Here's how to transition like a pro:

• Start with properly fitted swim shorts that have quality mesh liners
• Try it in private first – test the waters (literally) in your own pool or shower
• Focus on the benefits – better performance, comfort, and durability
• Invest in quality – cheap swim shorts without proper liners make the experience worse

Expert Recommendations and Best Practices

Swimming instructors, dermatologists, and pool maintenance professionals all agree: skip the underwear. The consensus is clear across multiple fields that directly deal with swimming and water activities.

Dermatologists particularly emphasize the importance of allowing your skin to dry properly after swimming, which is much harder to achieve when you've got multiple layers of wet fabric clinging to your body. Prolonged moisture near the vaginal area can upset your body's natural pH and bacterial balance—creating a perfect storm for yeast to grow. That's why quick changes after swimming or sweating can go a long way in preventing issues.

Pool professionals consistently report that cotton fibers from underwear are one of the most common causes of filter problems, leading to more frequent maintenance and higher chemical usage. If enough fibers travel in a cluster, they can get into your pool's filter and back it up. The filter will either stop working entirely or only barely work.

The Bottom Line: Trust the Design

Look, swim shorts exist for a reason, and that reason isn't to serve as a base layer for your underwear collection. Quality swim shorts – especially our Ball Hammock® designs with their supportive pouch technology and moisture-wicking properties – are engineered to handle everything underwear does, but better and in wet conditions.

When you're ready to upgrade your swim game with properly designed shorts that eliminate the need for underwear entirely, check out our men's swim collection at shinesty.com. Our Ball Hammock® Pouch Underwear technology provides the support and comfort you're looking for, whether you're in the water or on dry land.

Trust us, once you experience the freedom and performance of properly designed swimwear worn as intended, you'll wonder why you ever doubled up in the first place. Your comfort, your performance, and frankly, everyone else at the pool will thank you for making the switch.

Frequently Asked Questions

Is it hygienic to wear swim shorts without underwear?

Yes, it's actually more hygienic to skip underwear under swim shorts. Quality swim shorts are designed with built-in mesh liners that provide the necessary support and coverage. Wearing underwear creates a warm, moist environment that promotes bacterial and yeast growth, while proper swimwear allows for better airflow and quicker drying.

What if my swim shorts don't have a built-in liner?

If your swim shorts lack a built-in liner, consider investing in quality swimwear with proper mesh liners, or choose compression shorts specifically designed for water activities rather than regular cotton underwear. Board shorts without liners are the main exception where additional support might be needed.

Will wearing underwear under swim shorts damage my underwear?

Yes, pool chemicals and saltwater are extremely harsh on underwear fabrics. Chlorine breaks down fibers and causes fading, while the constant wet-dry cycle weakens the material. Cotton fibers are particularly vulnerable to thread degradation in chlorinated water, leading to premature wear and tear.

Does wearing underwear under swim shorts affect swimming performance?

Absolutely. Underwear absorbs water and creates significant drag, reducing swimming efficiency by up to 40%. The extra fabric layer acts like a water-collecting parachute, making you slower and requiring more energy to move through the water. This affects swimmers of all skill levels, not just competitive athletes.

Key Insights

• Performance Impact: Wearing underwear under swim shorts can increase hydrodynamic drag by up to 40%, significantly reducing swimming efficiency and speed in the water.
• Health Concerns: Wet underwear creates an ideal breeding ground for bacteria and yeast, with bacterial growth occurring within minutes in warm, moist environments like wet swimwear.
• Design Purpose: Quality swim shorts are engineered with built-in mesh liners and quick-dry fabrics specifically to eliminate the need for additional underwear layers.
• Pool Maintenance: Cotton fibers from underwear break down in chlorinated water and can clog pool filtration systems, causing maintenance issues and potential filter failure.

Citations

• Hydrodynamic drag research confirmed by SciELO Brazil study showing underwear increases drag by up to 40% compared to proper swimwear, 2017
• Competitive swimwear drag reduction confirmed by Wikipedia and NASA Spinoff research on swimsuit technology, 2008-2025
• Bacterial growth in wet clothing confirmed by ABC News medical report and Norton Healthcare studies, 2013-2024
• Chlorine damage to cotton fibers confirmed by Bean Bags R Us and EcoStinger fabric research, 2021-2025
• Pool filter damage from cotton fibers confirmed by Backyard Pool Guy and Tucann America studies, 2021
• Medical recommendations for avoiding wet clothing confirmed by Welia Health and Piedmont Healthcare, 2024-2025

Take the Next Step with Shinesty

Now that you know the truth about ditching underwear under swim shorts, it's time to experience what properly designed swimwear can do for you. At Shinesty, we don't just make swim shorts – we engineer aquatic excellence with our signature irreverent style that'll have you looking like the pool legend you were born to be.

Our swim shorts feature everything you need and nothing you don't: built-in mesh liners that actually stay put, quick-dry fabrics that won't leave you soggy for hours, and designs so bold they practically come with their own theme song. Plus, if you love the idea of premium comfort extending beyond the pool, our Ball Hammock® Pouch Underwear brings that same revolutionary support to your everyday adventures.

Ready to upgrade your swim game and join the ranks of guys who actually know what they're doing in the water? Visit Shinesty and discover why thousands of customers have ditched the double-layer struggle for good. Your pool performance, your comfort, and honestly, everyone who has to look at you in swim shorts will thank you.