key to the entrance

[tienhua]

I am just started out. I was swimming and trying to find the key to entrance of the cave. I am having problems in findding the key. Can someone help me?
Thanks

[Otherworld]

if you're talking about the grotto tutorial quest, you have to dive down in the middle of the room. Just jump in, point your camera at where you want to go and go forward. Pick up the key and press spacebar to surface quickly.

EDIT: the key is at the bottom of the cage. Just point your camera down and go forward.