Amphibious seaplanes have long been popular for sport flying, offering access to waterways as well as airports, but a new design from the start-up MVP Aero promises to expand those capabilities, creating a more boatlike aircraft. The two-seat airplane—introduced as a full-scale mock-up at July’s EAA AirVenture Oshkosh, the world’s biggest aviation event—will offer a unique deck-like platform that pilots can use to cast for fish or pitch a tent, for example. The MVP—for “most versatile plane”—will be able to mo…