Do You Wear Underwear With Swim Trunks? The Definitive Guide

Key Insights

• Why men wear underwear with swim trunks: Protection against sand, chafing, and accidental exposure from waves make underwear appealing, though it comes with drawbacks like fabric deterioration and introducing bacteria to pools.
• Best alternatives to underwear under swim trunks: Ball Hammock® Pouch Swim Trunks provide built-in support with quick-drying fabric that eliminates the need for separate underwear while preventing chafing and unwanted exposure.
• How swim trunk design has evolved: Traditional mesh linings felt like wet underwear, leading men to go commando under board shorts or wear boxer briefs for support, creating the underwear-under-swimwear dilemma we face today.

To commando, or not to commando? That is the question. For millennia, guys have faced a dilemma when heading to the beach or the pool: What do I wear under my swimsuit? Wait, so maybe THAT is the question? Hmm… Gimme a second to sort this out. Ok here’s the ACTUAL question: Do you wear underwear with swimming trunks?

Men's Guide: Should You Wear Underwear with Swim Trunks?

For women, this is usually a non-issue. It’s pretty rare to see a woman wearing a bra under her bikini top. Heck, sometimes in the summer women wear bikini tops AS bras. Unfortunately, wearing swimsuit bottoms as underwear when you’re not at the beach is still generally frowned upon for both men and women. Just do laundry already, bro.

The Evolution of Men's Swim Trunks: A Brief (Pun Intended) History

A lot of guys grew up during an era when men’s swim trunks had a mesh lining built in. This offered briefs-like support as well as protection from chafing. Unfortunately, after getting out of the water while wearing a mesh liner, it felt like you were walking around in wet underpants for an hour until they dried.

After mesh went out of style, guys generally went commando under their board shorts. While these swim shorts were certainly more stylish, there was also a huge increase in butt crack visibility every time a wave hit you. This is the pivotal point in human history when a lot of guys started wearing underwear under their swimming shorts.

What's Best Under Swim Trunks: Boxer Briefs or Going Commando?

Of course, boxer briefs weren’t the only option. Wearing a Speedo under your swimsuit was seen as a more fashionable alternative. After all, women’s bikinis come in two pieces, so guys were just getting away with wearing a two piece swimsuit where both pieces were bottoms. Unfortunately, if you’re a guy who prefers wearing swim briefs in the first place, it’s tough to cram a pair of underwear under that Speedo.

Why Your Swim Shorts Need Proper Support (Hint: It's About Comfort)

There are plenty of good reasons why men want to wear an extra layer under their swim trunks.

1. Sand. Sand belongs at the beach. Not in your crack.
2. Sand. Ever looked at sand under a microscope? It’s made of crushed up sea shells. Does having tiny shards of sea shells scraping against your junk sound like a relaxing day at the beach?
3. Chafing. Very few of us can afford swimsuits made of silk or velvet. Bottom line is things are gonna rub against the inside of your trunks (or at least the tips of things) and that’s gonna lead to uncomfortable chafing on the one area of your body that should never be chafed.
4. Waves. Water is more powerful than you think and can rip a swimsuit clean off your body. Underwear is a great way to avoid the embarrassment of running back to the car with your hand over your dick.
5. Water Slides: Water slides have the opposite problem as waves. Waves want to tear your suit OFF your body, but the force of going down a water slide at terminal velocity tends to wedge your suit IN your body. Underwear gives your cracks and crevices a shield against rogue underwear, while also preventing the unfortunate condition known as “water slide enema.”

The Dark Side of Men’s Underwear

Of course, there are downsides to wearing underwear under a swimsuit. For starters, I hope it’s not a pair of underwear you like. Because whether you’re in the ocean or a swimming pool, those things will begin to deteriorate immediately from the saltwater or chlorine.

And if you’re in a swimming pool when that underwear is deteriorating, the cotton fibers are gonna ruin the filter. And do you wanna risk calling the hot pool guy over to fix things while your wife is tanning on the chaise and you’re stuck at work late? That’s a recipe for disaster. PLUS, after they run off together, you’re gonna have to find a brand new pool guy because you can’t slack off when it comes to pool maintenance.

Finally, do you know what’s all over your underwear? Butt bacteria. And now it’s all in your pool. Open your eyes underwater? Boom. Pinkeye. Accidentally swallow a mouthful? Boom. E coli.

Types of Swim Trunk Liners

While we've explored the debate between going commando and wearing underwear under swim trunks, the real game-changer is the liner itself built into many swimsuits. Understanding the different types of liners can help you make an informed choice about what additional support you might need.

Mesh Liners: The OG Ball Cage

The classic mesh liner is like that friend who means well but doesn’t quite understand personal boundaries. Sure, it tries to help by providing some support and keeping your goods from flopping around like a fish out of water—but at what cost?

These netted nightmares are everywhere in traditional swim trunks. The idea behind them was simple: create a lightweight layer that adds coverage and keeps things contained without holding onto too much water. Sounds great in theory, right?

In reality, mesh liners tend to do the exact opposite. They trap sand, chlorine, and sweat against your skin, turning a fun day in the sun into a gritty, swampy mess. And when that rough netting rubs against your most sensitive real estate for hours on end, there’s only one possible outcome: Chafe City, population: your balls.

Compression Liners: The Sausage Casing Approach

Some upscale swim trunks throw in compression liners—think of them as glorified spandex boxer briefs fused to your swimwear.

These liners are more than just snug; they’re designed to support your muscles, reduce shaking, and improve recovery. Clinical studies on compression wear (not necessarily swim-specific, but relevant) demonstrate reduced muscle vibration and soft‑tissue displacement during activity, potentially minimizing fatigue. One such study showed that wearing compression garments “reduced lower‑limb muscle displacement and soft tissue vibrations” during running.

And while that sounds fancy, unless you're training for the Olympics—or avoiding flashing the kiddie cannon at the pool—the main perk is straightforward: compression keeps everything locked down tighter than Fort Knox. Meaning users reported fewer unplanned ball appearances mid-sprint or mid-swim.

But let’s talk reality: tight support is a double-edged sword. Compression liners can be comfortable for short bursts or athletic use, but wear them too long or too tight, and welcome to the ball-squeeze zone—more “compressed pastry” than “supportive casing.”

Removable Liners: The ""Choose Your Own Adventure"" Option

Removable liners are like the Switzerland of swim-trunk design—neutral, flexible, and here to keep the peace. They give you total control: snap them in when you want extra support, take them out when you don’t. It’s basically democracy for your downstairs.

The versatility is awesome, but once that liner comes out, you’re back to the classic debate: free-ball it or layer up? If you go the underwear route, don’t settle for damp cotton basics. Go for something built to handle the water, like Shinesty’s Ball Hammock® swim trunks, which have a built-in supportive liner made from breathable, quick-dry fabric. They keep everything secure and comfortable—without the scratchy prison-net vibe of traditional mesh.

With removable liners or built-in comfort, the goal is the same: keeping your boys happy, supported, and ready for whatever your pool day throws at you. Browse Shinesty’s full lineup of men’s swim trunks to find the perfect fit for your summer adventures.

Caring for Swim Trunks with Built-in Support

Whether you prefer classic mesh, removable liners, or built-in comfort like Shinesty’s Ball Hammock®, taking care of your swim trunks helps them last longer and stay comfortable. A little regular care goes a long way to keep your trunks looking good and feeling supportive, no matter how many pool days or beach trips they’ve been through.

Washing Your Ball Hammock® Swim Trunks the Easy Way

Your swim trunks deal with a lot—chlorine, saltwater, sunscreen, sand, and maybe even a spilled drink or two. Over time, these things can wear down the fabric and elastic. The good news? A few simple habits will keep your swim trunks in great shape without much effort.

1. Rinse after every swim
   Give your trunks a quick rinse with fresh water before tossing them in your bag or laundry basket. This helps wash away chlorine, salt, and sand so they don’t sit on the fabric and break it down.

2. Wash in cold water on a gentle cycle
   Hot water and harsh cycles are tough on elastic and can cause it to lose its stretch. Stick to cold water and a gentle wash setting to help your trunks hold their shape and support.

3. Air dry, don’t tumble dry
   Skip the dryer, which can damage elastic and fade colors over time. Lay your trunks flat or hang them in a shaded, well-ventilated spot to dry naturally.

A Little Care Goes a Long Way

Taking a few minutes to rinse, wash gently, and air dry your swim trunks will keep them looking sharp and feeling supportive all season long. Treat them right, and they’ll keep you comfortable whether you’re lounging poolside or diving into your next adventure.

The Ultimate Guide to Choosing: Underwear with Swim Trunks or Go Without?

Ultimately, fellas, it’s up to you to weigh the pros and cons and decide for yourself whether you’ll wear underwear under your swim trunks. But whatever you decide, we’re here to help. First off, you’re gonna need a swimsuit.

Then pick yourself up some underwear. should probably buy one of the uglier prints since it’s gonna get ruined eventually.

Finally, if you’re still on the fence, we recommend our collection of swim briefs. Wear them as a swimsuit, or wear them as another layer under one of our other swimsuits.

OR, and this is the exciting part so we saved it for the third to last sentence: You can get the best of both worlds with our brand new Ball Hammock® Pouch Swim Trunks. These trunks are fully lined with a soft, quick-drying fabric designed to take all the punishment that regular underwear under a swimsuit can’t. Plus, the Ball Hammock® ensures your gonads won’t get pinched by rogue hermit crabs.

Remember the choice is yours. As is the chafe.

Stay Weird & Dive In

Frequently Asked Questions

Question: Do women wear underwear under swim shorts?

Answer: Women typically don't need underwear under swim shorts designed with built-in liners or mesh. However, for unlined swim shorts, quick-drying athletic underwear or swimwear bottoms underneath provide necessary coverage and prevent transparency when wet. Skip cotton underwear entirely—it stays soggy and creates visible panty lines faster than you can say 'wardrobe malfunction.'

Question: Can women wear men's swim trunks?

Answer: Absolutely! Women can wear men's swim trunks, which often provide more coverage and pocket options than women's swimwear. Size down 1-2 sizes from your usual women's bottoms for proper fit. The built-in liner might feel different, but many women prefer the extra security. Just be prepared for less contouring in the hip area and a straighter cut through the thighs.

Question: How do you know when it's time to replace swim trunk liners?

Answer: Replace swim trunk liners when the elastic becomes loose, the fabric turns thin or transparent, or you notice persistent odors despite proper washing. If the liner constantly bunches up, rides up, or creates uncomfortable pressure points, it's time for new trunks. Most quality swim trunks with proper care should give you 2-3 seasons before the liner surrenders to chlorine's cruel embrace.

Question: How do you keep swim trunks from chafing?

Answer: Chafing happens when wet fabric rubs against your skin, especially in saltwater, chlorine, or when sand gets trapped inside your trunks. To prevent it, rinse your swim trunks with fresh water after swimming to remove salt, chlorine, and debris, choose trunks with a smooth, supportive liner like Shinesty’s Ball Hammock® design to reduce friction, make sure they fit properly so they’re not too loose or too tight, and avoid wearing cotton underwear underneath since it stays damp and can make irritation worse. The right fit and fabric can turn a day of rubbing and discomfort into a day of easy, comfortable swimming.