Primeval (2007)

S2E4 Underwater Menace

After a boy vanishes into a drain just as an underwater Anomaly appears, Stephen and the ARC team scour the nearby canal for the aquatic beast responsible for the incident. However, Cutter believes the creature is lurking elsewhere. His intuition proves to be tragically accurate when Abby is abducted by futuristic Mer Creatures and imprisoned in a submerged cellar of a warehouse. Meanwhile, Cutter and Connor uncover unsettling evidence of a conspiracy brewing within the ARC.