snuba

noun

1. (uncountable)A combination of snorkeling and scuba diving where the swimmer uses the fins, mask, and breathing apparatus commonly used in scuba diving, but the oxygen tanks usually strapped to the back are instead attached to floating rafts that remain on the water's surface.

   “This isn’t scuba, or even snuba, but simply underwater walking!”

   “One raft will support two snuba-divers. ¶ […] Orientation for the snuba activity is usually about 30 min, followed by a 30-min undersea experience.”

   “A fun alternative in the sea is a “snuba” tour, where snorkelers can go underwater tethered by a breathing tube to an air-supply float on the surface.”