The influence of floating tire breakwaters on the ecology of coves was studied in Lake Carl Blackwell, a 1400-ha reservoir in north-central Oklahoma. Breakwaters, consisting of a single row of 18-tire modules, were installed across the mouths of 2 coves (8.5 and 9.8 ha). Wind, wave height, water temperature, transparency, suspended solids, turbidity, and sedimentation rate were measured during one 7-month period at windward and leeward sites in 2 experimental and 2 control coves. Populations of fish and benthic invertebrates were monitored in experimental and control coves for 2 years after construction of the breakwaters. At leeward sites, breakwaters reduced wave heights by 50%, increased transparency in both experimental coves and increased sedimentation rate in I cove. Slight differences in turbidity, suspended solids, and temperature between windward and leeward sides of the breakwaters were similar to differences between lakeward and shoreward areas of control coves. Floating tire breakwaters had little adverse environmental impact on the coves. Electrofishing suggested an increase in centrarchid fishes due to the breakwaters.