A standard school-issued one piece swimsuit (usually white, gray, navy blue or black) with a subtle skirt near the top of the crotch to allow water to flow through the surface. Sometimes, the wearer's name is printed or written in a white space on the chest area.

Some skirtless and low- and medium-leg swimsuits that come in the colors mentioned above are also regarded as school swimsuits (though they may be closer to racing-type swimsuits).

(Copied from Danbooru)