Ariel the Little Mermaid is an Action & Adventure game released on the Sega Game Gear in 1991, where you must help either Ariel or her father Triton stop the evil Ursula from turning everyone into small, green worm-like creatures. The ones you don't initially choose are also affected by Ursula's spell.
The main goal of the game is to rescue your friends, which involves swimming into them as they hang out at fixed places in the underwater world. You'll need to fend off and dodge enemies like eels, clams, sharks, and other sea creatures while avoiding getting caught. Along the way, you can call upon friends like Flounder and Sebastian for a little assistance.