Seaplanes

Getting a traditional seaplane out of the water and into the air requires a lot more energy than getting a land plane airborne. First it must break that water suction and push itself up onto the step, then, balanced on its boat hull, accelerate. The trouble is, once it is airborne, it has to stop being a boat and try to fly. Now a high speed boat hull has the aerodynamics of a brick; it is all sharp edges and ledges and these create turbulence. A Seaplane has to suck this thick layer of turbulent air along much the same as if it were dragging a parachute. The drag penalty is large and the payload penalty is significant.

Seaplanes are used because landing on water opens up a vast number of destinations, most of them remote from any land airfield.
Amphibian aircraft are used because of their wonderful utility. Conventionally constructed airfields, of which there are about 18,000 in the USA, compliment their seaplane capability.

The approximate payload penalty for a general aviation seaplane is the equivalent of two passengers. This large penalty relegates seaplanes and amphibians to specialty work only. Unless you really need the seaplane capability you do not buy one.