Fire Island Inlet, located on the south shore of Long Island, N.Y., connects the Atlantic Ocean with Great South Bay. The inlet is about 3 miles long and approximately 1/2 mile wide, extending generally east and west between Oak Beach on the north and the western end of Fire Island on the south. Great South Bay, to which Fire Island Inlet is the main entrance, is a tidal body 25 miles long and 2 to 5 miles wide with a general depth of about 6 to 25 ft at m1w. Attempts have been made to stabilize an entrance channel through Fire Island Inlet with little success. To study this problem a fixed-bed model (later converted to a movable-bed model) was constructed to scale ratios of 1:500 horizontally and 1:100 vertically, reproducing all of Fire Island Inlet and a portion of the Atlantic Ocean. Tides, tidal currents, and wave action in the Atlantic Ocean were reproduced. Results indicated that the plan originally recommended by the New York District, which included a littoral drift trap located in the entrance to the inlet, a rehandling basin in the inlet, a connecting channel of adequate depth for navigation by a loaded hopper dredge, and a 500-ft extension to the Federal Jetty. The construction of groins, deflection dikes, and closure dikes would not appreciably improve conditions obtained by the recommended plan alone. A plan involving an offshore breakwater and a littoral drift trap located between the breakwater and the beach would also function satisfactorily in every respect. (Author).