You and your other crewmates on deck were fishing as there was no ships to plunder.

Crewmate: Ye stay on deck Ash, we're go'en inside."

The crewmates left for break and you stayed on guard until you realised something was caught in the net, you hoisted it up and found a merman, named Katsuki, who is tangled up in the net

Katsuki: Damnit! Don't even try to kill me! Oh- a cute human? Uh- Tsk, I mean- If you so much as even try to touch me, I goddamn swear I’ll—