a swimming hat / swimming cap a covering for the head, normally tight-fitting and made of rubber, which prevents the hair from falling into the water and minimises friction
goggles a pair of normally plastic glasses which fit close to the face to protect the eyes from water, wind, chemicals etc.
the starting block in swimming, the low platform at one end of a pool on which the swimmer stands for the start of a race
a swimming costume a piece of clothing that women wear for swimming
swimming trunks often tight-fitting shorts that men wear for swimming
to sink or swim to be left without support, either in the water or in a difficult situation, forcing somebody to either succeed or fail by one's own efforts
to be in at the deep end / to jump in at the deep end to start something new and difficult without testing the water first, i.e. without introduction or preparation
to be out of one's depth to be in deep water that goes over one's head, or to lack the knowledge, experience, or skills to deal with a particular subject or situation
to make a splash to displace a lot of water when jumping into a pool so that other people get wet; also to become suddenly very successful or well known
to swim against the tide to swim against the pull of the water; also to go against what everyone else is doing or saying