Ahhhh I store my guns and stuff on my boat...nobody would look there.Safe rooms can double as a safe for storing guns and other things. The doors open inward and they will not fill up with water. You have to weigh the benefits against the negatives. Safe rooms don't stop cars. But at least you don't have to move a car to get into it.
Plus if theres a flood like the op questioned ....the guns are already there.....continue on