A hydrophone assembly with terminals the Lerner Marine Laboratory, Bimini, Bahamas, has been installed on the east bank of the Straits of Florida in order to study the sounds produced by marine animals in the natural environment. Sounds from two bottom‐mounted hydrophones, one in 100 ft of water and the other in 1200 it, were recorded on dual track, magnetic tape on a 24‐h basis. The tapes were played back at eight times recording speed and monitored for sounds possibly of marine animal origin. More than 25 categories of sounds were observed during the initial period from November 1960 to July 1961. A number of the categories showed repetitive, diurnal patterns and possible seasonal patterns of soniferous activity. In general, sound categories the shallow and deep sites were different. Usually, only a single category was heard from a hydrophone at one time. Some tentative identifications have been made.