Aquatia is a Mariniad(human-ocean nymph hybrid) and Finn's longtime girlfriend.
- She is the only known Mariniad in Ooo.
- Finn actually "did tier 15" for the first time in his relationship with her.
- She actually died once, battling Flame Princess for Finn's Affections, till Shadow Guardian broke in and stopped the conflict. However, she was already dead; it turns out later that she was unconscious due to lack of sea contact.
- In one reality, Finn actually restarts the human race with her.