The movie "Umizaru" is the story of 14 young Japan Coast Guard officers who take part in a grueling training to become rescue divers. They must endure and survive a 50-day training. Daisuke Senzaki (Hideaki Ito) and 13 other recruits take part in the training. With his love for the ocean and dream to work as a rescuer at sea, a rescue diver seemed like the perfect occupation for Daisuke.

While a menacing typhoon approaches, an accident at the giant natural gas plant Regalia occurs. Japan Coast Guard rescue divers Daisuke Senzaki (Hideaki Ito), Tetsuya Yoshioka (Ryuta Sato) and engineer Hiroshiichirou Sakuragi (Masaya Kato) head together to the gas plant. During their rescue efforts an explosion occurs that traps Daisuke, Natsu Nishizawa Kazue Fukiishi and worker Hisayoneo Kizima (Gaku Hamada). Daisuke then looks for a way out for his party with a man he just meets Takuya Hotori. Because of the typhoon, even a helicopter cannot approach the Regalia. Meanwhile, at the head office of the Japan Coast Guard, the Japanese coast guard tries to find a way to rescue the trapped people, but the government officials put national interests first. Tension arises between these two parties. Daisuke's wife Tamakisai Senzaki (Ai Kato) prays for the safe return of Daisuke not only for her sake, but for their new born son.

Mika is a flight attendant on board an airplane scheduled to land at Haneda Airport. On the way to the airport the airplane's engine starts to burn. In order to save the 346 people on board the airplane, sea marshall Daisuke Senzaki and his team are called into action ...

A small team of Coast Guard divers, including Daisuke, rappels onto the ship from a helicopter and begins to evacuate the panicked passengers. Then Daisuke finds a familiar face - Kanna. They had a tiff the night before about their wedding plans - Kanna had already made her dress, while Daisuke was still reluctant to propose - and she left for Tokyo, feeling like a fool. Now she see Daisuke in a different, more heroic light - but before they can properly reconcile, she has to evacuate, while Daisuke searches for stray passengers.