Use the arrowkeys to control the submarine, read the ingame hints/instructions carefully.
Buy a floodlight and thats all you need. In one of the maps you waste your battery so you need to peddal. If you peddal and get eaten by a shark, keep peddaling and you should live.
Then get all the treasure on the map.
Map and location of items on land:
You must press A to get off of the map whether you changed Routes or not.
Nalani Route - Seaman's Cove, Tabaco Isle, Dolphins Creek.
Maka Koa Route - Corall Village, Mermaid Bay, Neptunes Island, Seaman's Cove.
Alohi Route - Corall Village, Whales Home, Turtle Isle, Dolphin's Creek.
Seaman's Cove - battery pack x2 $8500.
Tobaco Isle - plating $8000; battery pack $7500.
Dolphins creek - oxygen $7000,8000.
Corall Village - Sell seagrass.
Mermaids Bay - Save.
Neptunes Island - floodlight $7000; oxygen $9000.
Whales Home - medium propeller $6000; large propeller $8000.
Turtle Isle - plating $7000.
Locations of treasure maps:
Maka Koa map 1 - Under Corall Village on the left in the dark.
Alohi root map 2 - Near Dolphins creek in the dark, not in the tunnel to the right.
Nalani root map 3 - Directly below Seaman Cove, Second ledge in the dark.
Dolphins wil show you where the treasure is.If you stop driving he wont tell you so folow him.