The Ocean Hunter is played by using two mounted turret-like guns on the arcade cabinet. The game is capable of being played with either one or two people simultaneously. The player takes the role of an underwater adventurer searching for the Seven Great Monsters of the Seven Seas, hoping to collect on the bounties placed on their heads for attacks on shipping vessels, humans and native marine life. The player proceeds to go throughout the game in a set path, shooting at various hostile ocean life along the way. The game is played progressing through various levels, each with its own design and layout. Upon reaching the end of the level, a boss is encountered. Each boss is named after a famous mythological sea monster: Kraken, Leviathan, Charybdis, Ahuizotl, Karkinos, Midgardsorm, and Rahab. There are also dozens of mini-bosses in the game, many of them also named after sea monsters.

A new civilization is flourishing in the seas of an alternate Steampunk world, but giant ocean monsters are attacking shipping vessels, harbors, humans and native marine life with increasing frequency. Ordinary marine predators such as sharks have begun to follow in the sea monsters' wake to scavenge what they could from the destruction caused. Frightened for their lives, the people issue bounties on the monsters' heads. The underwater adventurers Torel (Player 1) and Chris (Player 2) head out to defeat the horrible creatures.