Aerial surveys, out to 222 km off the east coast of central Florida during August 1980, revealed that marine turtles were distributed in a narrow zone west of the Gulf Stream. Of 255 loggerhead turtles, Caretta caretta, only three were observed east of the western boundary of the Gulf Stream. Radiometric thermometry revealed that the waters occupied by most Caretta were markedly cooler than the nearby waters of the Gulf Stream. Of 18 leatherback turtles, Dermochelys coriacea, all were seen west of the Gulf Stream in waters less than 70 m in depth. Marine turtles off eastern Florida are confined seasonally to nearshore waters west of the Gulf Stream. The records of Dermochelys in nearshore waters are in contrast with a deep water oceanic ecology often hypothesized for this species.