swimming equipment

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

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