We examined effects of body size and temperature on swimming performance in juvenile estuarine crocodiles, Crocodylus porosus, over the size range of 30–110 cm total body length. Swimming performance, expressed as maximum sustainable swimming speed, was measured in a temperature- and flow-controlled swimming flume. Absolute sustainable swimming speed increased with body length, but length-specific swimming performance decreased as body length increased. Sustained swimming speed increased with temperature between 15°C and 23°C, remained constant between 23° and 33°C, and decreased as temperature rose above 33°C. Q₁₀-values of swimming speed were 2.60 (± 0.091 SE) between 18°C and 23°C, and there were no differences in Q₁₀ between crocodiles of different sizes. The broad plateau of thermal independence in swimming speed observed in C. porosus may be of adaptive significance by allowing dispersal of juvenile animals at suboptimal body temperatures.