here's the situation.
a LCT carrying a DD tank becomes fast aground before it reaches shore. Heavy surf is in play. Immediate immobilization if a non-waterproofed vehicle unloads into a shallow ocean heavy surf location.
Can the DD tank claim it's screen is up if it offloads from a LCT.
The rules don't seem to seem to say either way in this case. They seem to be written for entering the game with screen up already in amphibious mode.
Since we are the middle of a game, I'll take a good reality argument in lieu of an official answer.