snuba

Noun

 * 1)  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.
 * 2) * 2001, Christie Stilson, Maui and Lanaʻi, Ninth Edition, Prima, ISBN 9780761529576, page 400:
 * This isn’t scuba, or even snuba, but simply underwater walking!

Usage notes
Snuba diving is known in tropical tourist locations such as Hawaii.