The key is in a level on the game Puffle Rescue in the mine. You get to chose a pink, blue or black puffle but you need to click on the black one. What you do is you go to where the puffle is on the first level and wait for the squid to cast its shadow on the water and it will send bubbles up so you don't sink. Keep going on top of the bubbles until you get to a platform. There should be a vent that blows air and you swim right until you see a passage way(stairs) and what you do is go into it and the key should be there unless you already have it.
The hidden lake is underground in Club Penguin. Here's how to get there:
You need to play Puffle Rescue located underground where you play Cart Surfer. Select the black puffle to rescue and you can get to the hidden lake by getting the black key. You need to be a member to do the black puffle though.
I Think You Mean "The Hidden Lake" Not "The Hidden River". First, You Go To The Mine. Then You Go To The Mine Shack. Next, You Go To The Cave Mine. Then, You Look Towards The Right Of The Screen And Their Will be a Cave Entrance. Enter The Cave, And Congratulations! You've Just Arrived In The Hidden Lake!
go thourgh the cave or go thourgh the hidden entrance in the forest
You have to play the black Puffle mission in the Puffle rescue game (members only) and follow the squid.
u gotta have amethist
the mine
The Hidden Lake
it is on the hidden lake in the lake down
In the mine
Hidden Lake.
in the hidden lake
Go to hidden lake.
Hidden lake
on top of hidden lake
at the hidden lake!
you dont
i just play