tomboyx | Premium Underwear for All Day Comfort. Fit for You.

Swim 4.5" Shorts

Swim 4.5" Shorts - Main image
$38.88 $54 In stock

Category: swimwear

Reveal an aquatic surprise with our water-activated fabric. When dry, black keeps its secrets hidden. But splash some water on it, and watch as gray jellies emerge.

How It Works

Our innovative color-changing technology responds to water contact. The moment moisture hits the fabric, the previously invisible jellyfish print transforms from black to gray. Once dry, the fabric returns to its sleek, all-black appearance—ready to surprise again and again.

Not to brag, but this is the perfect length swim bottom. Coverage? Great fit? Something that won't ride up or slip down while wet? Welcome to swim bottom nirvana.

Sustainability note: We recycle 7 water bottles to make each 4.5" short

  • Mid rise fit, 4.5" inseam
  • Water activated - black when dry and jelly print when wet
  • UPF 50
  • Smooth, durable flatlock seams won’t irritate or chafe
  • Shell: 80% recycled polyester; 20% spandex
  • Lining: 88% polyester, 12% spandex
  • OEKO-TEX® Certified
  • Inclusive sizing from XS-6X
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Standard Shipping: Handling (business days) 0–1; Transit (business days) 7–15.

Express Shipping: Handling (business days) 0–1; Transit (business days) 7–15.

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Delivery costs

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Standard Shipping · United States: $0.00

Express Shipping · United States: $3.99

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Returning an item

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United States · Return window (days after delivery): 30. Return method: By mail. Return postage: Seller pays.

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Customer Reviews (5.0 / 5 · 5 reviews)

Sofia ★★★★★

Took these to the beach yesterday and couldn't stop grinning when the gray jellies faded in as I waded in. The fabric feels sturdy but light, and the surprise never got old every time I splashed myself.

Evelyn ★★★★★

The water-activated jelly reveal is such a fun surprise—my kids couldn’t stop splashing me to see them appear again. The fabric dries back to plain black quickly, so the magic never gets old.

Edward A. ★★★★★

The dry-to-wet trick got me grinning like a kid—dunked them at the beach and the gray jellies popped right out. Fabric feels sturdy enough for laps, not just lounging, and they dried fast after the swim.