Free! dj - Little Mermaid in Love

From September Scanlations:

Pairing: Haruka x Rin

[Future Fish AU] Rin is a police officer who's had to give up his dream of Olympic swimming in the wake of his father's death and family's worries that he'll also be 'taken away by the sea', until a strange man washes up on the beach, with no memories and no voice, and Rin is reminded of things he'd rather not have remembered.