Deep Sea Party (深海パーティ, Shinkai Pāti) is the eighteenth episode of the anime series, Full Metal Panic!
Summary
Kaname is nervous when Sousuke asks her to go to a secluded island with him, but is less enthused when the island turns out to be Mithril's base. An emerging situation forces Sousuke to immediately report to the Tuatha de Danaan with Kaname still in tow. When she arrives aboard the Tuatha de Danaan, she is surprised at the royal treatment she receives and is invited to the submarine's first anniversary party.