What Is The Difference Between An Amphibian Plane And A Seaplane?
The primary difference between the two is in the type of landing gear. An amphibian plane has a set of retractable wheels, which enables it to take off and land on both land and water. A seaplane, which has pontoons but no wheels, is limited to water takeoffs and landings. And because its pontoon landing gear cannot retract, a seaplane is less aerodynamically efficient than an amphibian plane.
Sources: Encyclopedia of Aviation, pp. 172-73; World and United States Aviation and Space Records, p. 138.