Directed by Joe Dante Written by Richard Robinson   John Sayles   Cast Bradford Dillman ... Paul Grogan Heather Menzies-Urich ... Maggie McKeown (as Heather Menzies) Kevin McCarthy ... Dr. Robert Hoak Keenan Wynn ... Jack Dick Miller ... Buck Gardner Barbara Steele ... Dr. Mengers Belinda Balaski ... Betsy Melody Thomas Scott ... Laura Dickinson (as Melody Thomas) Bruce Gordon ... Colonel Waxman Barry Brown ... Trooper Paul Bartel ... Mr. Dumont Shannon Collins ... Suzie Grogan Shawn Nelson ... Whitney Richard Deacon ... Earl Lyon Janie Squire ... Barbara Randolph Roger Richman ... David Bill Smillie ... Jailer Guich Koock ... TV Pitchman Jack Pauleson ... Boy in Canoe Eric Henshaw ... Father in Canoe Robert Vinson ... Soldier Virginia Dunnam ... Girl Diamond Farnsworth ... Water-skier (as Hill Farnsworth) Bruce Paul Barbour ... Man in Boat (as Bruce Barbour) Robyn Ray ... Screaming Woman Mike Sullivan ... Dam Guard Jack Cardwell ... Brandy Uncredited Cast Sally Bondi ... Swimming Deb Eric Braeden ... Dr. Robert Hoak (swimming double) Joe Dante ... Scuba Diver #2 Amy Holden Jones ... Hertz Clerk R.C. Keene ... Beach goer Andrew G. La Marca ... Scuba Diver #1 John Sayles ... Army Sentry Phil Tippett ... Scuba Diver #3 (victim) Produced by Roger Corman   Jon Davison   Jeff Schechtman   Hisako Tsukuba   Original Music by Pino Donaggio

Additional Info Premiere: August 03, 1978 DVD Release: October 26, 1999 Blu-ray Release: August 03, 2010 Country: Distributor: Scream Factory Websites: Production Companies Piranha Productions New World Pictures Distributors New World Pictures   (1978) (USA) (theatrical) National Broadcasting Company (NBC)   (1980) (USA) (TV) (broadcast premiere) Warner Home Video   (1983) (USA) (VHS) Buena Vista Home Entertainment   (2006) (USA) (DVD) Shout! Factory   (2010) (USA) (DVD) (special edition) Shout! Factory   (2010) (USA) (Blu-ray) (DVD) Fangoria Presents   (2015) (USA) (theatrical) (Ultimate Edition) New Concorde   (1999) (USA) (DVD) Viacom   (1989) (USA) (TV) (syndication) Rating Stats Overall Rating 5.4 / 10 Our Rating 4.8 / 10 Your Friends -- / 10 Male Users 4.8 / 10 Female Users -- / 10 Site Ranking #3,402 / 20,725 Ratings Breakdown Almost Perfect 3 total ratings Average 1 total rating Crap 2 total ratings Site Ranking #3,398 Captivity (2007) #3,399 Goosebumps 2: Haunted Halloween (2018) #3,400 Storm Of The Century (1999) #3,401 Below (2002) #3,402 Piranha (1978) #3,403 Supergirl (1984) #3,404 I Am Not Your Negro (2016) #3,405 Shivers (1975) #3,406 Junebug (2005)