Primeval (2007)

S5E2 The Submarine

While on a mission in the North Sea, a Navy submarine uncovers a massive underwater Anomaly. Matt, Connor, and Abby board the vessel to assist the crew, but trouble arises when the submarine is suddenly dragged through the Anomaly into a prehistoric ocean filled with enormous pliosaurs. The team frantically works to return the submarine to their own time, all while Lester battles to prevent an Admiral from launching a nuclear strike on the Anomaly, which could drastically change the course of history.