With this gold, you can upgrade your weapon, ammo, speed, powerups, health, and energy. There are also two upgrades that can sharpen your propeller to do damage to fish and a light for when it gets dark down below.
Your goal is to dive down and find a treasure chest at the bottom of the ocean. Depending on the level, there are also other objectives that you must complete before you can pick it up such as to kill a certain amount of fish with your harpoon. As you progress on to harder levels, the ocean’s depth gets deeper and the levels get harder.