A guide on how to use the iDiver app to upgrade Dave's equipment, including the optimal upgrade path for maximum efficiency.
Upgrades in Dave the Diver cost Gold (which you earn by running Bancho Sushi at night). To actually purchase an upgrade, you must be on Cobra's boat during the day. Open your in-game Smartphone and select the iDiver App. From here, you can select which piece of gear to enhance. Since you will need a lot of money to max out your gear, check out our Best Ways to Farm Money Guide. Below is the optimal priority order for your upgrades.
Your Air Tank is the most important piece of equipment in the game. Oxygen acts as both your dive timer and your health bar. The more oxygen you have, the longer you can stay underwater catching fish, and the more damage you can take from aggressive predators without dying. Always upgrade your Air Tank first!
Your Cargo Box dictates how much weight you can carry. If you exceed this limit, Dave becomes encumbered—he will swim incredibly slowly, burn through oxygen much faster, and become an easy target for sharks. Upgrading the Cargo Box allows you to carry more high-value fish back to the surface, which directly increases your nightly restaurant revenue.
Upgrading your Harpoon Gun increases its base damage, allowing you to catch larger fish more easily. While this is helpful, it is a lower priority than Oxygen and Weight. This is because you should primarily be using actual firearms (like the Hush Dart or Net Gun) to catch fish alive for 3-star quality, rather than relying solely on the Harpoon.
Your Diving Suit allows you to explore deeper sections of the Blue Hole without taking crush damage from the water pressure. However, there is no reason to upgrade your suit early in the game! Only upgrade the Diving Suit when a main story quest explicitly requires you to dive deeper. Spending money on it prematurely will leave you starved for gold when you actually need it.