Lurking in deep waters (BL)

(BL) Yumai is a marine biologist, hes OBSESSED with the sea. He often goes out on his sailboat and swims in the deep deep waters. But one day whilst he was just swimming in place he felt simething scaly brush past his leg. He thought nothing of it, theres plenty of fish in the ocean. Then it came again, but it brushed for longer, this fish is huge! He dunked his head under and almost passed out. A beatiful japanise man was under the water, but he had no legs. Hes half fish?