Only members can get it because you can only get it on the black puffle level in puffle rescue. If you are a member then go on to this level and wait for the shadow. When it comes past you will see bubbles, you must jump on these to give you air. If you stay on one bubble too long it will pop and you will loose air (it took me ages to get across!) Soon you will come to this island and i think you will stairs. Go down them and you will come to a small cave. Lying near a huge shell you will see a key, pick it up. Now whenever you go to the hidden lake just click on the door in the pool and you will be in the secret cave!
If you mean the one by the underwater cave you have to follow the squid on the first level of rescue the black puffle there is a squid follow it and you will come to a door which the key is hidden in.
You will get the key when you have rescued the black puffle in puffle rescue three times it does not work
key
You can buy a club penguin guide book. Then, look in the content for key merchandise and go to the page.
You go to the mine. You then play puffle rescue. Then play the black puffle version. Then you follow the octupus in the first level and find a secret room to get the black key and a key.
The Hidden Lake
in the library
in the hidden lake
In the lighthouse beacon.
If you mean the one by the underwater cave you have to follow the squid on the first level of rescue the black puffle there is a squid follow it and you will come to a door which the key is hidden in.
You completely finish the puffle game and you get a key.
go on puffle rescue on the black puffle and follow the squid
Play puffle rescue on the black puffles and find the key on the first level
You will get the key when you have rescued the black puffle in puffle rescue three times it does not work
the game in the mine shack not cart surfer but somthing else it was like this cool penguin saving puffles
go to the puffele rescue and the type what you just wrote in youtube
No. i think you can with a cheat my friend has it and he isn't a member it might be something else though