For me, it would be because of a great ("great" as in Ed Wood style film-making) movie "The Monster that Challenged the World" (even the title seems low budget).

https://www.imdb.com/title/tt0050722/

tl;dr "An earthquake in the Salton Sea unleashes a horde of prehistoric mollusk monsters. Discovering the creatures, a Naval officer and several scientists attempt to stop the monsters, but they escape into the canal system of the California's Imperial Valley and terrorize the populace"