Nanatsu no Umi no Tico

A young girl named Nanami moves in with her father, a marine biologist, aboard a research vessel. Her father is searching for a mysterious creature called the Glowing Whale. After discovering its bones, he shifts his focus to protecting these beings. Nanami forms a bond with an orca she calls Tico, swimming with it daily. She develops the ability to breathe underwater, surprising her father. During one incident, she nearly drowns but is rescued by a Glowing Whale, which brings her back to the ship. Her father witnesses the creature during this event.