Finn is a young merboy appointed to keep the electric storm eels from escaping their prison into the open Never Sea. But one day he accidentally released one with the power of his trident.
Finn first appeared in the episode "Mer-Matey Ahoy!", when he introduced himself to Jake's crew its his duty to keep the Storm Eels lock away in special cave beneath the Never Sea, but one of the eels manage to escape his watch when his trident set it lose. Jake and his crew offer to assist Finn return the Electric Storm Eel back to its cave. But the Electric Storm Eel proved to be quite slippery even with Jake's and his crew assistance accidentally getting Bucky entangled in a large bed of seaweed. Meanwhile Captain Hook manage to steal Finn trident to unlock a hidden treasure deep beneath the Never Sea. But this is short live as the massive Electric Storm Eel collides with Hook's sub causing it to sink forcing the captain and crew to abandon it leaving Hook and his crew at drift in the middle of the Never Sea only for Jake and his crew accompanied by Finn to rescue them and reclaim the trident. Electric Storm Eel soon reappeared to mock Finn for failed attempts to catch him, Jake soon noticed the Storm Eel's playful nature, and devised a plan with Finn's assistants to have it chase them back to the Eel's cave. With Electric Storm Eel trap behind its cave Finn thanks his new friends before heading off the check on the other Storm Eels caves.
- Finn is noticeably the first merman to appear in both the spin-off and the Peter Pan franchise.
- He is the only mermaid which tame at least 2 wild animals.