How do I get into the lighthouse?

Hint 1 of 12:

Did you notice the key on the floorboards?

Hint 2 of 12:

Well, that's not the key to let you get into the tower.

Hint 3 of 12:

But you might want to try draining the lighthouse.  See the first question
in this section for more help with this.

Hint 4 of 12:

That chest below might have something important in it.

Hint 5 of 12:

Unfortunately, there's no key for the chest.

Hint 6 of 12:

Or perhaps there is.

Hint 7 of 12:

The key that you see on the floor above is the key to the chest.

Hint 8 of 12:

Maybe you should try to get the chest to float to meet the key.

Hint 9 of 12:

It's filled with water right now.

Hint 10 of 12:

But if you open the spigot, the chest will empty.