Piranha

Man has once again manipulated nature, and this time the result is not only deadly… it's ravenous! On a calm, delicious night, two young hikers decide to take a moonlit swim in the peaceful waters of Lost River… unaware that they are about to become the feast of a species of man-eating piranhas! Their deaths trigger an investigation that uncovers a secret government experiment known as Operation Razorteeth. But worse is yet to come. This insatiable and macabre army of monsters is moving downriver, where a new summer vacation resort has just opened its doors… and will provide them with a feast of vacationers unless a brave ecologist (Bradford Dillman) and a beautiful, intelligent researcher (Heather Menzies) stop their deadly advance… for good.