Full Metal Panic! 3rd Section: Into the Blue

Original title: フルメタル・パニック！イントゥ・ザ・ブルー

When Sousuke invites Kaname on what seems like a trip to a tropical island, they instead find themselves aboard the Mithril's submarine. Their journey takes a dangerous turn when Gauron, the terrorist believed to be dead, resurfaces and hijacks the vessel, forcing Sousuke and his allies into a desperate fight for survival.