The game begins underwater, where Ariel can shoot bubbles to trap her foes and throw them. She can also dig through sand to find treasure and pick up sea shells to break open treasure chests. Treasure chests contain power-ups to increase her bubbles' power and range. Ariel can collect icons scattered throughout the levels to restore health, gain extra lives, or increase the range/power of her bubbles. The gameplay is similar to other Capcom games such as Chip 'n Dale Rescue Rangers and DuckTales.
When a stage begins, Ariel descends from the top of the screen to the recommended starting point in the NES version, but just starts out in the recommended position in the Game Boy version. The featured SFX are different in both versions. The start of the stage's BGM can be heard only once in the NES version; although the whole BGM can be repeated in the Game Boy version. The stage backgrounds were more restricted in the Game Boy version than in the NES version. When you lose a heart, the heart turns into a heart frame in the NES version, but disappears in the Game Boy version. The key scales of the Boss BGM are different in both versions. The BGM speed in the NES version is much faster than in the Game Boy version.
In the introductory cutscene, Ariel is in her human form and plans to wed Eric. Upon learning that the sea-witch Ursula plans to take control of the ocean, Ariel leaves Eric to become a mermaid once more and sets off to rescue her underwater friends.