You play as a cat living on a tiny island with nothing more than a small shack, a mailbox, and a little boat that's barely holding together. Thankfully, it's still good enough for your favorite pastime, fishing. Since this is an upgrade-driven game, you'll be spending plenty of time out at sea if you want to catch every fish the ocean has to offer.
Fishing is simple because you just need to click anywhere to fire your harpoon, ideally straight into a fish. You don't have to wait for the harpoon to reload before firing again, but every shot uses some of your oxygen, which is also constantly draining while you're underwater. Every fish you catch earns you money, although you'll quickly discover that some species are out of reach or have skin too tough for your current equipment. You might get lucky and catch the fish when it’s close, where the harpoon strength is strongest, but if you don’t do it on your first try, it will swim away.
Back on the island, clicking on the shack lets you upgrade your gear. Oxygen tanks simply increase your air capacity, while harpoons improve in several different ways, including range, oxygen cost, fire rate, and penetration. Upgrading boosts every stat at once, although you can also save your money for an entirely new harpoon type. One example is a shotgun harpoon that fires three projectiles at once, trading much higher oxygen consumption for greater coverage. Oxygen tanks follow a slightly different progression. Once you fully upgrade your current tank, you can pay extra to unlock a better model and start upgrading it from scratch.
Money lets you buy only four harpoon types, while another eight require special parts instead. These advanced weapons are noticeably stronger and often come with unique abilities. One fires a homing fish, while another continuously shoots harpoons as long as you hold the button. Eventually, you'll need one of these anyway because every harpoon can only be upgraded ten times, and the basic model simply won't be enough to catch everything.
The shack also lets you upgrade your boat, allowing you to reach more distant fishing grounds where the catches are worth far more. You can also purchase three consumable items that make fishing easier. Bait attracts nearby fish to a single spot, a net catches multiple fish at once, and an electric bomb stuns everything in the area. All three have limited uses, so you'll need to keep buying replacements.
Parts are much harder to obtain because they come from rarer, more valuable fish. Every location contains several different species, but which ones appear depends on the number of waves, something determined entirely by your oxygen capacity, as well as daily chance modifiers that can increase or decrease certain fish spawns. You can check the current day's effects by clicking the calendar icon. Parts are also awarded for completing an area's fish collection, although you can buy them from a traveling merchant who occasionally visits your island if you're willing to pay the steep price.
There are a few other ways to earn rewards as well. The mailbox sometimes contains a newspaper along with a little money each day, and a small cat, who is probably your kid, hands out fishing quests. These usually ask you to catch specific fish several times before rewarding you with money or parts.
Once you reach day 25, you unlock an aquarium where you can spend money and parts to fill it with fish and decorations. Decorations increase the aquarium's capacity, although you can only place a limited number of them. Fish provide experience, with rarer and more valuable species generating more. You can only purchase fish you've already caught at least once, giving you another reason to complete your collection.
This introduces the game's idle progression. Fish generate experience every real-world hour, even while you're away. Whenever you gain enough experience to level up, you receive rewards such as new fish, decorations, money, or parts. If you're impatient, you can spend parts to speed up progress toward the next level, although the cost quickly becomes very high. The best part is that the aquarium keeps working even when the game is closed, so there's no need to leave it running in the background. Better yet, your cat even catches a few fish while you're away, making every return to the island feel worthwhile. But because of that, the game is very grind-based, and it will takes days and days until you get enough parts for a better harpoon or even a new boat.
