Shinryaku! Ika Musume

Synopsis

A beach volleyball tournament is held with a 3D television as top prize and Squid Girl and Eiko decide to team up, managing to reach the finals against Gorou, who has teamed up with Tatsuo Isozaki. When Eiko twists her ankle during the match point, Chizuru takes her place and wins the competition. Later, Squid Girl's tentacles suddenly stop working, along with her other squid abilities, and the others try various methods to bring them back with no avail. Although the others suggest it would be alright if Squid Girl returns to the sea, everyone becomes lonely when she does not immediately return. Squid Girl later returns with her tentacles cut off, residing herself to being a normal girl, though Takeru makes it clear this is not what makes her happy. As Squid Girl laments on the beach, she meets a girl named Kozue Tanabe, who assures her not all humans are bad and that she is not alone. As Squid Girl and Eiko go swimming in the sea, they are caught in a whirlpool caused by Harris, Clark, and Martin, and Squid Girl's desire to save Eiko causes her tentacles to grow back, allowing her to rescue Eiko from drowning.

(Source: Wikipedia)