On a cruise around the Mediterranean the weather takes a turn for the worse. The Regal Princess encounters a semi-submerged boat, calling upon the captain to make some critical decisions. It's the first time new officer Lauren has had to deal with an emergency on board and she must keep constant watch on the wreck as it threatens to disappear amid three-metre swells, while a rescue team poises itself for action. Elsewhere on board, the adverse conditions disrupt a magic show and threaten to make one young British couple's wedding a washout.