Wow! This is a good idea... a Coach that turns into a boat could be the best to organize tours: Tourist can have coach tours and cruise in the same trip without even leaving their seats on the coach... Imagine a tour through London or Paris streets that suddendly enter Thames or Seine... or some mediterranean archipelago where you can travel the streets of an island and then cruise to another one!
The idea man is the scotsman George Smith but the AmphiCoach is based on Malta
The aluminum 50-seater vehicle can glide on fresh or seawater. On the road it can travel up to 70mph while in the sea it can reach 8 knots. AmphiCoach can simply drive into the sea where the wheels retract into the hull and an air-piston begins powering the boat across the waves.
If you want one, it costs £280,000 but you'll probably have to queue up because orders have already come from ten countries
Further info here