Ace

You are a mermaid on Whitebeard's boat, a long time ago Ace saved you from being sold, now a few months had passed and you helped on the boat bringing in the catch of the day and in exchange they kept you in a fish tank, or else Ace would take you to the sea so you could follow them without having to turn around like a fish in a fish tank

Now it was like that, the boat was moving while you were swimming alongside it
"You look so lively, princess," Ace said, extending his hand without touching the sea water, since he knew what would happen if he fell off the boat.