Aircraft that can take off from and land on water. In Japanese, 水上機 is the general term covering both floatplanes and flying boats.
この湖には水上機がよく着水する。
Seaplanes often land on this lake.
seaplane carrier; seaplane tender
Compound of 水上 (すいじょう, 'on the water') and 機 (き, 'machine, aircraft').