It's pretty fun once you max out all the upgrades and not gonna lie, I'd say that managing oxygen and swordfish become harder with more upgrades because of collision tracking making it so that it's more likely your shots get blocked by something the more efficient at killing fish you become, so in a way, it's interesting how the endgame doesn't just get rid of all the difficulty, but forces you to be a bit more careful with your shots. I wish it was more obvious the upgrade tab was scrollable and that harpoons were just autofire, because they're endless anyway so the only thing limiting their rate of fire is wrist pain or hand pain.