The ocean is bustling with many big and small fish — and also sharks. However, only the one who catches the biggest fish may keep it. When sharks show up, the big fish are in danger, so whoever then fishes for the small fish fishes best. If the species happen to match, a big catch of many fish is possible.

Hi Fisch! starts with 36 cards face down around a large sandbank tile. On ten of the cards, a shell token is placed. Each round the players flip over a card one by one. If a shark is revealed, a player has to turn another card until a numbered fish is revealed. Shell tokens are moved to the sandbank tile.

If after revealing the cards a shark card is face up, the shark eats the highest numbered fish (both cards are discarded). The player who turned over the highest numbered fish collects all shell tokens, the fish card, and all cards of the same species (if present). The remaining fish cards are turned face down again, then a new round starts.

When only six or fewer face-down fish cards are present, the game ends and the final score is calculated. Each shell or fish is one point, except for the small, hard-to-catch green fish, which are worth two. The player with the most points wins.