Twilight Princess...Im in The Forest Temple and im collecting the damn monkeys. I am having trouble at 2 bits...

1 there are 3 bridges which alternate and i can seem to get across if it is possible

2 i have an addiional monkey to get but the key is below. Its the room with the springy monsters under the ground and when you light the lanterns it raises the ground. Is it possible to lower the ground by exinguishing the lanterns somehow? There is water in the room but i dont know how to collect. The key must open that cage because you can only use the keys in the same room.