Is it this one
https://www.mangago.me/read-manga/utakata_no_uroko/
If not you can search in this tag
https://www.mangago.me/tag/Merman/
Unfortunately that’s not the one and I’ve gone through the tag and couldn’t find it(/TДT)/
Funnily enough the manga you shared was the one that made me recall this manga I’m looking for hahaha.. at this point I don’t event know if this manga even exist but I can clearly remember the whole plot….
Thanks for the reply though, appreciate it

Looking for a human x merman manga where they met when they were kids and mc would spend most of his time with the merman boy near the shore. Mc’s family warns him of the danger since a boy has drowned and was never found.
Merman’s dad opposed of his relationship with mc and would send ominous weather when they meet. He stop meeting mc and they drifted apart. As they grow older, mc never stops going to the shore and purposely gets in the sea so that the merman would save him every time. Mc begs to turn him into a merman and they ended up together.
Pls help been thinking of this manga for days now ╥﹏╥