1) Bather 2) Explorer of the depths 3) Natator 4) Skin-diver 5) Swimmer 6) Undersea explorer 1) Oceanaut 2) Skindiver 
An aquanaut is any individual who remains underwater, exposed to the ambient pressure, long enough to come into equilibrium with his or her breathing media. Usually this is done in an underwater habitat on the seafloor for a period equal to or greater than 24 continuous hours without returning to the surface. The term is often restricted to scient...
[n] - a skilled worker who can live in underwater installations and participate in scientific research
aquanaut 1. Somebody with training and equipment to spend long periods working or swimming underwater. 2. An undersea explorer; especially, one who skin-dives from or lives for an extended period of time in a submerged dwelling.
noun a skilled worker who can live in underwater installations and participate in scientific research
an undersea explorer, esp. one who skin-dives from or lives for an extended period of time in a submerged dwelling. · a skin-diver.