Lynn Poole discusses some of the reasons for underwater research: studying alewife fish in Lake Hopatcong, NJ; researching predator fishes; harvesting agar from seaweed for iodine, ice cream gelling agents, and other uses; and obtaining magnesium from the sea. Cartoons illustrate historical diving gear and models show current masks, snorkels, and fins. Jacques Cousteau and Emile Gagnan developed the regulator and diving suit, which became synonymous with SCUBA (self-contained underwater breathing apparatus). Divers from Johns Hopkins's Chesapeake Bay Institute model both warm and cold weather diving gear, and Dr. Carritt, researcher at the institute, explains how an oceanographer uses SCUBA to investigate such underwater activities as the health of oyster beds. In a film clip, scientist-divers explore the Gulf of Mexico's bright oily crescent for Saucony-Vacuum and Magnolia Oil Companies. A diagram shows the anticline, fault, and stratigraphic oil traps of this region.