How do I cross the reservoir?

Hint 1 of 4:

A full-sized yacht would help.

Hint 2 of 4:

No dice. You can't get across it from the south.

Hint 3 of 4:

Read the game's hint.

Hint 4 of 4:

You can get to the north side by going down the whirlpool in the waterfall
cavern. Make sure not to take anything but your lamp.