How to Choose TomboyX Swim Bottoms for Your Body

Quick answer

Start with the coverage you want, then choose the closure and lining. Want more thigh coverage and a secure waist? Pick a lined board short with a drawcord or elastic waist. Want the least bulk and fastest changes? Choose an unlined pull-on trunk. For swim briefs, size by your usual underwear waist first, then adjust for packing or compression layers.

Decide coverage before you look at size

Coverage is the first filter because it changes how the bottom feels when wet and how much chafing protection you get. A 9-inch inseam board short covers more of the thigh than a 7-inch trunk, which matters if your thighs touch or you plan to walk around after swimming. A shorter trunk gives more airflow and dries faster but leaves more skin exposed to sand and sun.

If you want swim bottoms that can double as everyday shorts, a longer board short with a lined interior works better than a brief or trunk. If you mainly swim laps or want minimal fabric, a shorter trunk or brief is easier to move in.

Choose lined or unlined based on how you swim

Lined swim shorts include an inner layer, so you can wear them without separate underwear and get a consistent feel in the water. Unlined shorts are lighter and dry faster, but you may want to wear swim briefs underneath for support or packing.

The tradeoff is drying time and packability. Unlined trunks take less space in a bag and feel less bulky when wet. Lined shorts add a layer that can hold more water but give more coverage and structure.

Match the waistband and closure to your dexterity and activity

Pull-on styles with a fully elastic waistband and no zippers or hardware are the easiest to get into and out of, especially with wet hands or limited dexterity. Drawcord or hook-and-loop closures stay put during vigorous swimming but take more effort to adjust.

If you paddle, dive, or swim in waves, a secure closure reduces the chance of your shorts slipping. If you mostly lounge or wade, a pull-on waist is simpler and more comfortable.

Size for the swim layer, not your street clothes

Swim bottoms should fit snugly without cutting in, because fabric relaxes in water. Use your waist measurement as the starting point, then check the size chart for the specific style, since a 9-inch board short and a 7-inch trunk can fit differently. If you plan to wear a swim brief under an unlined short, size the brief to your usual underwear waist and the short to the brief, not the other way around.

For packing brief sizing, choose a brief that holds everything in place without compression. If you want extra support, a swim compression top can pair with high-waisted bottoms to keep layers from shifting.

Check the return and try-on plan before you commit

Try swim bottoms on over clean underwear at home before getting them wet. Check that the waistband stays put when you squat, that the leg openings don't ride up, and that the inseam doesn't bunch. If you're between sizes, size up for board shorts and stay true to size for briefs, then return the one that doesn't work.

If you're shopping for plus size swim bottoms, look for styles with a wide, stay-put waistband and enough rise to cover your stomach comfortably. The same coverage rules apply, but fabric stretch and waistband height matter more.

Your step-by-step swim bottom fit check

1. 1. Measure your waist and hip: Use a soft tape at your natural waist and fullest hip, then compare to the size chart for the exact style you're considering. Checkpoint: if you're between sizes, size up for board shorts and stay true to size for briefs.
2. 2. Pick coverage: 9-inch, 7-inch, or brief: Choose a 9-inch inseam for maximum thigh coverage, a 7-inch trunk for less fabric, or a brief for minimal coverage. Common mistake: choosing a shorter inseam for style, then finding it rides up when you swim.
3. 3. Decide lined or unlined: Lined shorts can be worn alone; unlined shorts are lighter and dry faster but may need a separate swim brief for support. Checkpoint: if you want one-and-done, go lined; if you want packability, go unlined plus a brief.
4. 4. Check the waistband and closure: Pull-on elastic waists are easiest with wet hands; drawcords or hardware stay put better in waves. Common mistake: ignoring dexterity needs and buying a fiddly closure you'll dread using wet.
5. 5. Try on over underwear and move: Squat, lunge, and raise your arms to check for pinching, riding up, or gaping at the waist. Checkpoint: if it shifts now, it will shift more in the water.
6. 6. Pair with a top or compression layer: If you wear a swim compression top, choose high-waisted bottoms so the layers overlap and don't roll. Next step: test the full outfit in the shower before your first swim.

Product facts to know

• Swim 9" Lined Board Shorts Heavy Weight: Swim 9" Lined Board Shorts Heavy Weight have a water-activated print that changes from black to gray when wet, then returns to black when dry. You get a lined 9-inch short with a hidden print reveal, which is useful if you want more thigh coverage and a fun detail without changing your fit.
• Swim 7" Pull-On Board Shorts Light Weight - Marine Mosaic: Swim 7" Pull-On Board Shorts Light Weight - Marine Mosaic are unlined with a fully elastic waistband and no closures, zippers, or hardware. This is the easiest style to pull on and off, and the unlined build dries faster if you pack light or change outdoors.
• 9" Boxer Briefs: 9" Boxer Briefs are the longest cut, made with a soft cotton blend and a stay-put waistband that is fit-tested on all body types. If you want a longer under-layer for chafing protection under unlined swim shorts, this cut gives more coverage than a standard brief.