A quick guide on the most valuable and important fish you should always hunt for when exploring the Blue Hole.
Always try to kill or capture sharks. Their meat serves as the base for many of the highest-selling dishes in the game, and they frequently drop necessary crafting materials (like shark teeth) for weapon upgrades. Use a Hush Dart or Net Gun if possible to catch them alive for 3-star quality meat!
Moray Eels are unique because they only come out of their hiding spots during Night Dives. Moray Eel Curry is highly profitable and is actually required to complete Otto's VIP quest to unlock the farm. Don't forget to dive at night to stock up on these.
Tuna swim extremely fast in schools and can deal damage if you get in their way. You usually need a Sensor Net Trap or a high-level Net Gun to catch them efficiently. Because Tuna dishes fetch incredibly high prices at Bancho Sushi, they are a massive source of income when properly enhanced.
While they can be annoying to fight (and often require a sniper or harpoon to safely dispatch), jellyfish are crucial for the Jellyfish Party event. Stockpiling them early is one of the easiest ways to make a massive lump sum of money in the early game.
Always keep your Bug Net handy! Catching tiny seahorses, shrimp, and other small critters doesn't use up much of your precious weight capacity, but they are essential for filling out your Marinca collection app. Later in the game, specific high-tier seahorses are required to win the Seahorse Racing mini-game.