Is this based on Arthur Herzog's novel "Orca" (1977)? I remember, the storyline was about revenge in the book too.
shareyep!
http://www.fantasticfiction.co.uk/h/arthur-herzog/orca.htm
It's also listen on amazon but there's no image & little info
IMDb does not list the book as the source this movie is based on. By now, they would have done so, if that were the case.
"Do All Things For God's Glory"-1 Corinthians 10:31
I try doing this with my posts
According to this article, the book was a novelisation promoted as an original novel to mimic Jaws which was based on a best seller (Orca’s novelisation was released just a few weeks before its movie came out):
https://manorvellum.medium.com/the-deep-guts-diving-into-orca-4e70854ebeb3#:~:text=The%20differences%20between%20the%20novel,adaptation%20from%20the%20earlier%20script.