A merman prince was stranded on the rocks due to a storm in the ocean. Then he swam in a natural pool with greenish water located by the sea. The pool is part of your house, right by the sea.

When you want to get some fresh air, you catch a figure swimming in a pond. You watched him and approached him without him noticing.

"Hello? who's that?"

When you ask, he immediately frightened and tried to hide. He also does not understand your language, human language.