In the stampede scene we notice that the pelican who steals the game leave through a big hole in the wall! Later in the movie the whole house is flooded by a monsoon! What happened to the hole in the wall! How did the house get filled with water?
You do have a good point about the hole in the wall. But think about this, wasn't that strange vine/ivy stuff always growing thicker and stronger? Perhaps it covered the hole enough so that it could hold a lot of water inside the house, while only leaking a little through the holes.
Well my take on it all is that if the game can do all these things including creating a stampede that put a hole in the wall, then if the game wants them to drown in an in-house monsoon, then it will do that and it will make it that it is possible to do that. So basically I rekon the game fixed the wall so they could drown.
If you remember correctly, when they left the house they showed a small clip of those killer plants growing on the wall. I think that these killer vines covered up the hole in the wall.