How do you open the door in club penguin in the hidden lake?

Answer 1

You need to be a member.

You play the Black Puffle Rescue game, and on the first level, collect the puffle.

Then wait. In the background, you should see a black shadow. Follow it, collecting the bubbles it makes to stay afloat. You will end up in the coral reefs. Explore for a bit, and go down the staircase you see.

The game will end, and you will be in the Underground room. The Key is there, which means you can enter the underwater room, at any time. since i cant can u do it for me i will give u my penguin name and password

Answer 2

you just walk in to it but you have to make sure that its in a clear space