One of the most common float-plane accidents is forgetting to retract the nose-wheel(s) before setting down on water. The nose-wheel digs in and you do the world's smallest front loop!
The simplest way to prevent nosing-over in the lake is to never install a nosewheel.
You could probably get away with a fixed tail-wheel undercarriage if it only extended a little below the keel. That would restrict you to landing on only the smoothest asphalt runways. You would have to "pitch" the airplane precisely to avoid scraping the keel.
The tail-wheel would be so far aft and produce so little drag that it would make little difference on landing.
Burt Rutan hinted at a similar concept last year, but Burt refuses to publish drawings or pictures until after he has test-flown his retirement project.
Another way would entail installing a fixed main wheel just aft of the step. Then install a retractable ski/step just ahead of the main-wheel. If you inflated an air-bag to extend the ski/step, it would auto-retract is you forgot to retract the step when landing on asphalt.
Something as important as lowering/raising wheels really should include two or three ways of confirmation during the pre-landing check-list. Hard-wired retraction handle (e.g. solid control rods linked directly) Many float-planes jus flop their nose-wheels on top of their bows when they retract. The pilot can visually confirm that at least one nose-wheel is up-and-locked. Speaking of visual confirmation, have you noticed the little, convex mirrors hanging from wing struts on lots of floatplanes. Those mirrors allow pilots to see under their floats to confirm wheel position.
Fancier amphibians sport a variety of instruments or warning lights across the top of the instrument panel. The fanciest amphibians have "*****ing Betty" horns that nag about wheel position an time you retard the throttle to flight idle before the wheels are locked.
