yeh thanks i think i realised the first bit i made it too tricky. Aj and co played the playalong on Wednesday and they found it easy so i made it trickier, possibly too much. 

If u go to the water dispenser,  a hand sign appears on the wall, then collide with this for the door to open to reveal the key.

And yes maybe i should build a secret tunnel from the aquarium, but currently its just ornamental