swimcap

This term refers to a specialized piece of athletic equipment designed for hydrodynamics and hygiene. While often associated with competitive swimming to minimize water resistance, it is equally common in recreational settings to prevent hair from clogging pool filters.

Depending on the material, such as silicone, latex, or lycra, the connotation shifts from professional performance to casual comfort. It is a compound noun that is consistently used in the singular when referring to the item of clothing generally, but can be pluralized when discussing inventory or a group of swimmers' gear.