How do you get the key to the door in the hidden lake in club penguin?

you have to be a member to get the key......go to the mine and play puffle rescue with the black puffle.....on level 1 get the puffle and wait will see a squid ..go on the bubbles it produces onto the island ..go through the door in the island.. you will find yourself in a room .then you will spot the key ..pick it up and go to the hidden lake and enter ... you will find the room