If all drain holes work normally, some water should be no problem. Most computer shelves also have covers with drain tubes attached. E.g rain entering the cabin through the entry door or cargo door on freighters. However here also lies the problem: how many drain holes are full of debris or iced up after a longer flight...
A flood of water is always to be considered dangerous. I remember that we once had to shut down all elec power and take out every computer to let it dry, after the aircraft was flooded in a heavy rain storm with doors open. The aircraft had some flights after that with a lot of the computers needed to be replaced.
Last edited by Piper19; 20th Feb 2014 at 12:20.