I've read like 5 chapters of it only and a long time ago at that. Is it this one???
https://www.mangago.me/read-manga/incident_name_tsunami_killer_whale_hunting_method/
Found something else that sounds like the description you gave. Is it this???
https://www.mangago.me/read-manga/orca_mansion/

I suddenly remembered this manhwa that's about a killer wale and small golden fish it's BL, but I don't remember the name? Σ(っ°Д °;)っ