a person who swims underwater using scuba-diving equipment

The goosander or merganser.

The dabchick, or little grebe.

A fish, the sand darter.

Someone who skin-dives.

(mythology) A common character in various traditional creation myths who is sent by a supreme being into the primal waters to find substance (often sand or mud) with which to build habitable land.

Someone who takes part in cave diving

Gavia adamsii, the largest member of the loon or diver family, having a black head, white underparts and checkered black-and-white mantle.

Gavia arctica, a medium-sized member of the loon or diver family that breeds in Eurasia, with grey head, black throat, white underparts and chequered black-and-white mantle.

Gavia stellata, the smallest member of the loon or diver family, breeding in northern Eurasia and Arctic Canada, with grey head, red throat, white underparts and dark mantle.