how much water?

[RonB]

it's about 24 inches to the bottom of the front door, I imagine that's one of the reasons they said 20. I've been in 30 to 36 inches (briefly) and no worries. There are all sorts of seals/valves that may not be designed for u-boat missions.
I heard about an H2 that blew the computer in the mud pit here in Gorman and had to be towed out. I think he hit it pretty fast and it can be fairly deep during the winter months.
This guy dove right in with his family. He was lucky somebody was nearby with a winch. When his wife opened the door about 8 inches of water came pouring out.