Has anyone considered putting a hydrofoil on a sea plane?
Yes. I mean, sort of. Nobody's ever built a production hydrofoilplane.

It's not a bad idea, but seaplanes are a relatively niche product these days and there doesn't seem to be a lot of innovation in the field. Back when there was, there was innovation everywhere so the idea of hydrofoils didn't stick.

The Convair F2Y Sea Dart, a 1950s prototype jet-powered fighter, used two 'hydro-skis' for takeoff and landing. It was more or less awful compared to the crop of land-based aircraft coming along and after a prototype disintegrated they (probably wisely) chose to shut the program down.



There are some other prototype aircraft that used actual hydrofoils that I found after some quick googling. A company called Lisa Airplanes seems to have an LSA - the Akoya - that's under development using tech similar to the Sea Dart.

The 1929 Piaggio P.7 used hydrofoils, and was intended to compete for the Schneider Trophy, but never made it airborne. Interestingly enough it had a screw (marine propeller) at the tail and a proper aviation propeller up front, and the pilot would've had to do some juggling between the two.



It's likely there were others, but I'm running low on sleep.