Cheat mode:
Press Start during game play to view the sonar screen. Press Right, 1, 2, 1, 2, Down, 2, Up to display a new menu with invincibility, unlimited continues and other options.

Level	Password
Medusa Bay	QMBRB
Undercaves	AGCFU
Ridgewater	VADJR
Open Ocean	QYEKR
Cold Water	IAFWN
Deep Water	YAHWV
The City of Forever, part 1	OKBKI
Origin Beach	CCRIJ
Dark Water	WGUKK
The City of Forever, part 2	MEMSK
The Tube	GGWAO
The Machine	KOWMP
The Vortex	WCSKQ