You can watch this online from the Internet Archive:
Ferdy on Films (dead link as of 4/28/2012) gives it a nice treatment, including some photos, and says,
I enjoyed it just as much on viewing it now as I did as a kid. ... this film is a solid genre piece filled with pleasures I was happy to experience again.Time Out closes with this: "Pretty ordinary (not to say ludicrous), but some inventive and brutal underwater sequences." DVD Talk says, "All the cliches and more are present" but notes Bava's work: "The film has good photography and some impressive matte work by Bava".