A diver is a person who works underwater, either professionally or recreationally. The term 'diver' can refer to a variety of different occupations, including a LOON (4 letters), which is a type of water bird that dives for food; a FROGMAN (7 letters), which is a type of military diver; a SEAL (4 letters), which is a marine mammal that dives for food; an AUK (3 letters), which is a type of seabird that dives for food; scuba (5 letters), which is a type of self-contained underwater breathing apparatus; and a SUBMARINE (9 letters), which is a type of vessel designed to operate underwater.