Shark in Venice (2008)

The seemingly tranquil waterways of Venice are terrorized by the perfect killing machine. In search of his father who has mysteriously disappeared diving in the city, David stumbles across the cryptic trail leading to the long-lost fortune of the Medici. As the unwitting pawn in a Mafia plot to recover the treasure, David's girlfriend is kidnapped at gunpoint, plunging him into a desperate race against time. If he has any hope of saving her he must enter the deadly waters. Can David out-gun the Mafia assassins and survive the voracious sharks laying in wait beneath the surface, or will he succumb to the same fate as his father?

Source: TMDb