During the last sixty years many attempts have been made to take photographs underwater at depths varying from just below low-water to many thousands of feet. The pioneer work of Boutan (1893) showed clearly that the essential requirements were a relatively light apparatus fitted with a good source of illumination. Ewing, Vine & Worzel (1946) gave a list of workers who have obtained underwater photographs at wading or diving depths. In their own work Ewing, Vine & Worzel have designed a number of underwater cameras with which they have taken some thousands of pictures of the sea-bottom. In their free-floating cameras the apparatus is allowed to sink to the bottom with a ballast weight. On touching the bottom a trigger sets off the camera which takes two pictures with a time interval of 30 sec. After this the ballast is released and a float brings the apparatus to the surface. In their suspended cameras the component parts are mounted, as in the free-floating cameras, on a vertical pole, with the camera near the top and a trigger at the base. Activation of the camera occurs when the trigger touches the bottom. Their most satisfactory light source proved to be the photoflash bulb. With one or other of these cameras they have obtained large numbers of clear photographs in depths ranging from 10 to 2400 ft., and have used these in studies of bottom deposits, sand ripples, and the distribution of animal life. (See also Ewing, Woolard, et al, 1946.)