Captain Sonny Jennings and his core team of lifeguards monitor the dangerous Hawaiian waters; new lifeguard recruits compete to join Sonny's district; Sonny and his family grieve after the loss of his nephew; Em reveals a romantic past with Will.

A flash flood sweeps a young tourist away from her family and out to deep sea; going against Sonny's wishes, Em takes a bold risk and places her own life in danger in hopes of rescuing the lost-at-sea tourist.

Em works to earn the team's respect when she is left in charge and Hina and Kainalu juggle multiple beachside emergencies; Will's fiancée pays him a visit at work; Sonny opens up to a former lifeguard about his trauma since losing his nephew.

College kids get trapped in a collapsed sandpit; Sonny, Will and Laka race to rescue people stranded after a shark attack; Will learns if he made the cut for the firefighter job he has been pursuing.

The lifeguards of the North Shore experience the most dangerous ocean conditions the district has seen in years; Sonny assigns Laka as acting lieutenant; Kainalu's father pressures him to leave his shift and help him with his campaign.

The North Shore community come together for Rocky's paddle-out; Hina thinks about switching districts; Laka, Will and Kainalu try to save a beachgoer that accidentally speared his own foot; romance heats up between Sean and Em.