Check out this pick-up ! http://www.youtube.com/watch?v=rXtaGPUFPr8&mode=related&search= I imagine they can also get there by reversing the procedure.
Hmmm ... :x Anyway - Notice how the ramp stays open till after takeoff - I imagine it's a necessary part of the procedure - ie. lets all the water drain out and door difficult to close when submerged.