The Killer Shrews

The Killer Shrews is a 1959 horror film directed by Ray Kellogg and released as a double feature with his Giant Gila Monster movie.

I found the giant shrews more believable than the duck walk to the shore.

1000 Misspent Hours calls it "one of the last great monster movies of the 1950’s" and says

Hiding beneath the bargain-basement special effects is an extremely economical, shockingly suspenseful movie, with unexpectedly complex characters, a fast-moving, engaging story, and quite a bit of imagination.

BMovieGraveyard has a page devoted to this movie that includes character sketches, a plot overview and walk-through of the film, still shots, and lots of commentary.