Larger feet are a genetic advantage for swimming but are in no way required. Like most other sports there is a body type that is advantaged in swimming. - Tal

Larger feet are a genetic advantage for swimming but are in no way required. Like most other sports there is a body type that is advantaged in swimming. - Tall overall height (max speed is limited by length at water line just like boats) - Lower than usual ratio for torso length to leg length - Large feet - Long arms (positive ape index) - Large hands Michael Phelps is a perfect example of this.