What to wear under a rash guard

Most people wear a compression shirt, t-shirt, bikini top, sports bra, or one-piece swimsuit under their rash guard. You can also wear a rash guard without anything underneath. The choice depends on your comfort level, support needs, and planned activities.

Rash guards provide excellent sun and surf protection on their own. But adding layers underneath can improve support, modesty, or warmth in cooler water.

We’ll discuss your options, from when you don't need anything underneath to choosing the right layering system for your water adventures.

SwimZip offers rash guards, swim shirts, and swimsuits to help you build a comfortable, stylish swim outfit that protects against UV rays through UPF 50+ fabric.

Why layer under rash guards?

Rash guards don’t require an underlayer in many situations. Boys and men usually just wear them without another layer. But girls, women, and people swimming in certain conditions add underlayers for a few reasons.

• Bust support: A sports bra or supportive bikini top prevents uncomfortable bouncing during active water sports.
• Modesty: Parents often prefer extra coverage for their children and themselves. Many rash guards are thin and tight enough to outline curves and nipples.
• Chafing: Seams and tight fits can cause chafing.  A thin layer underneath reduces irritation from seams or fabric texture.
• Water temperature: Cool lakes, early morning swims, and extended water activities are more comfortable with an additional layer.
• Transparency: Light-colored rash guards can become see-through when wet.
• Coverage: If you have a short-sleeve or cropped rash guard, an additional long-sleeve layer protects you against sunburn by covering your arms and core.
• Changing in public: If you want to take your rash guard off after swimming, an underlayer lets you change without heading to the bathroom.

Some rash guards feature built-in shelf bras and swimsuit liners that support and protect against chafing. If you’d rather not add an extra layer, shop for those features.

If you want or need an underlayer, keep reading to learn about your options.

T-shirts and compression tops

T-shirts and compression tops add warmth and allow for an easy transition out of the water. Avoid cotton since it bunches up and chafes when wet. Synthetic fabrics, like polyester, are more comfortable. For extra warmth, you can also buy compression tops with thermal properties.

Long-sleeve swim shirts under short-sleeve rash guards

Layering long-sleeve swim shirts under short-sleeve rash guards maximizes sun protection. This combination covers arms completely while maintaining the style and fit of your preferred short-sleeve design.

Choose thin, lightweight fabrics for base layers. Thick materials create too much bulk and restrict movement. The outer rash guard protects, while the inner layer adds comfort.

Bikini tops and sports bras

Bikini tops provide the support many women need under rash guards. Choose styles without excessive padding or hardware that create lumps under fitted fabric.

Triangle and bandeau styles suit regular and crop-style rash guards. Both options prevent wet transparency while maintaining comfort.

Choose sports bras for active water sports or large bust support. The secure fit stays in place during surfing, swimming, and beach volleyball. Look for quick-dry fabric that won't stay soggy between activities.

Shop colors that won't show through your rash guard. Neutral tones blend under most rash guard colors, while bright shades can create visible lines through light fabrics.

One-piece swimsuits

One-piece swimsuits provide extra support and comfort. They also serve as your bottoms. Try a scoop-neck rash guard with a high-neck one-piece for a stylish and modest ensemble. Add one of these to your paddleboarding or kayaking outfit for comfort and coverage.

What to wear with rash guards

Rash guards cover the upper body, so you still need swimwear bottoms. Try these options to build a beach ensemble that matches your style:

• Swim trunks, board shorts, and euro shorties are the main choices for boys and men. Shop below-the-knee options for better coverage and rash protection.
• High-waist bottoms create a flattering silhouette with cropped rash guards. They raise the perceived waist for a slimming effect and minimize the gap between top and bottom.
• One-piece swimsuits cover your bottom and form your rash guard underlayer. If you plan to lounge after exiting the water, they make changing out of your rash guard a breeze. They're also a stylish option for modest swimwear.
• Bikini bottoms let you show your legs, while your rash guard protects your vulnerable shoulders and arms from UV rays.
• Swimsuits cover the upper body down to the thighs. If you're shopping for your kids, front zip styles make dressing and diaper changes a breeze.
• Girls' and women’s swim skirts add feminine flair for a stylish, active beach outfit.
• Adult and children’s swim leggings offer full lower-body protection. Paired with a rash guard, you only need to protect your face, neck, hands, and feet with sunscreen.

Shop brands that use UPF 50+ fabric to protect your skin, since UV rays penetrate regular fabrics and cause sunburns. SwimZip's sun-protective swimwear covers you from head to toe in style, comfort, and UV protection.

Rash guard layers FAQ

Should I wear a bra under my rash guard?

Most women choose a sports bra or bikini top for support and coverage. Regular bras can cause bulges and snags, and they stay wet long after you leave the water. They also degrade from saltwater and chlorine exposure. Stick to performance swimwear.

What's the best option for large bust support under a rash guard?

Large bust support requires structured sports bras or underwire bikini tops. Look for quick-dry fabric for post-swim comfort and avoid excessive padding that creates bulk. Adjustable straps help achieve the right fit under fitted rash guards.

Do I need to wear anything under a zip rash guard?

Zip rash guard styles work with or without base layers. The zipper makes it easy to adjust coverage and ventilation. Many women prefer wearing bikini tops or sports bras underneath for style, comfort, and support.

What should kids wear under their rash guards?

Young children often wear swimsuits underneath for easier bathroom breaks. Boys’ and girls’ rash guard sets include separate pieces that coordinate and provide proper coverage. Older kids can follow the same guidelines as adults.

Can I wear a regular t-shirt under my rash guard?

Avoid cotton t-shirts. They get heavy and coarse when wet. Choose quick-dry fabric options instead. Compression tops are better than loose t-shirts because they don't bunch up or create drag in the water.

How do I prevent my rash guard from riding up?

A snug fit that isn’t overly tight prevents ride-ups. Choose the right size and shop for four-way stretch fabrics that move with your body.

What's the difference between a cropped rash guard and a regular-length rash guard?

Cropped rash guards end above the waist and pair with bikini bottoms or high-waist bottoms. Regular-length rash guards provide more core coverage and sun protection. Both work with the same base layer options.

Should I apply sunscreen under my rash guard?

Apply SPF 30 sunscreen to exposed skin. If you buy swimwear with UPF 50+ fabric, your covered areas will be protected all day.

Explore our complete collection of UPF 50+ sun-protective swimwear for safe sun adventures 🌊 

Further reading

Do rash guards keep you warm?

Rash guards vs swim shirts

Best rash guards

UPF vs SPF

What is the UV index today?