What makes a good swimmer?

The best swimmers tend to be tall and thin with long arms, long legs, long feet, and long hands. The size of their hands gives them great "water grasp", and only a very small hand movement keeps them afloat.

They also have great strength, endurance, insulation against heat loss while in water below body temperature, thus better energy conservation, low resistance when in the water, and swimming stroke mechanics (for example, shoulder and elbow joints that move very well, etc).