A hydrophone assembly has been installed on the east bank of the Gulf Stream, with terminals in the Lerner Marine Laboratory, Bimini, Bahamas. This assembly is being used to study the feasibility of combining acoustical, biological, and electronic techniques for information on soniferous animals in the natural environment. Sounds from two bottom‐mounted hydrophones, one in 100 ft of water and the other in 1200 ft are recorded on dual‐track magnetic tape on a 24‐hr basis. The tapes are played back at eight times recording speed and monitored for sounds of possible marine animal origin. More than 25 categories of sounds were observed during the initial period from November, 1960 to June, 1961. In general, sound categories at the shallow and deep sites are different. Usually, only a single category is present at a hydrophone at one time. A number of repetitive, diurnal patterns and possible seasonal patterns of soniferous activity are discussed. Some tentative identifications are made. Expansion of the installation is currently in progress; this includes additional hydrophones for the localization of sound producers and for information on migratory behavior of short duration. Demonstrations of the categories are presented from tape recordings. (This work was supported by the Office of Naval Research, the Bureau of Ships, and Bell Telephone Laboratories.)