Monster (1980) aka Monstroid (repost)

A rural Colombian village is attacked by a horrible sea serpent, aroused by industrial pollution of a nearby lake. Based on a real event that took place in June of 1971.

Directors:

 Kenneth Hartford (as Kenneth Herts) , Herbert L. Strock (uncredited)

Writers:

 Kenneth Hartford, Walter Roeber Schmidt, 2 more credits »

Stars:

 James Mitchum, John Carradine, Philip Carey - via IMDB 

https://archive.org/details/MonsterA.k.a.Monstroid