And a little plot summary from Wikipedia:
Off the coast of Alaska, oceanographer Emma McNeil (Deborah Gibson) is aboard a submarine studying whales when, without warning, a sonic device dropped from a military helicopter awakens a Megalodon (a gigantic shark) and a Giant Octopus from their 10-million-year slumber. In no time at all, both creatures wreak havoc all over the ocean, terrorizing oil platforms and mutilating whales on their way. The Megalodon destroys the Golden Gate Bridge and even devours a 747 airliner from several thousands of feet in the sky.
When several attempts at stopping both creatures from inflicting further damage fail, McNeil, Professor Lamar Sanders (Sean Lawlor) and Japanese scientist Dr. Seiji Shimada (Vic Chao) decide that the only way to stop the mayhem is to have the Megalodon and the Giant Octopus fight each other to the death. Allan Baxter (Lorenzo Lamas), a veteran commando, is assigned to lure both creatures out of civilization and stage their "Thrilla in Manila."
EDIT: F'ing hell that's a SPOILER! Some of us actually wanted to watch this crud you know!