Kid's Swim Trunks (Swimwear)

An elastic waistband, a drawcord threaded through it, an inseam often between 4 and 7 inches on children's sizes, and a mesh liner sewn inside are the four parts that define trunks. The liner does two jobs at once. It removes any need for underwear, and its open mesh lets water drain out in seconds instead of holding it against the body.

Fabric is woven rather than knit, usually a light polyester, often with a water repellent finish so the shell sheds rather than soaks. Woven cloth does not cling the way knit does, which is why trunks feel dry within twenty to thirty minutes on a warm day and why a child can wear them straight to lunch. That same weave rarely carries a UPF rating, so treat trunks as clothing rather than sun protection, and be aware that everything above the waist and below the hem is still bare skin.

Board Shorts are the nearest sibling and differ in three ways: longer legs, flat side seams and no liner. Most families pair them with a Rash Guard, since trunks leave the whole torso open. Speed and a child's ability to dress alone are what sell trunks, which is why they dominate pool bags from about age three onward.

Pool days, splash pads, camp and any morning a child dresses without help are what trunks were made for, and they double as ordinary shorts on the walk home. They fall short in three places. Loose weave holds water in deep pockets, which drags on a swimmer trying to cover a length. The mesh liner irritates some children, and cutting it out leaves a short that goes transparent when wet. Lap swimming wants a knit brief or jammer instead, since a woven leg fills with water and slows every stroke. Buy by pulling the drawcord tight and having the child jump. If the waistband slides below the hip on dry ground, it will come down entirely in water.