This is a ""survey"" of inner-space happenings starting with a brief history--did you know that in 1505 someone came up with sealskin submarines?--and continuing into recent experimental phases with Sealab I and Sealab II, revolutionary equipment, etc. and projections of future developments--""aquaculture"" for example. There is a helpful assortment of tips for the scuba and snorkeling buff and there are notes on underwater photography, hunting and treasure troving. This also details the author's archaeological expeditions. . . he helped discover an entire underwater city off the coast of Greece. For the more advanced wet suit surveyors who have 147 million square miles to conquer.