Lifeguards rescued 21 people on south shores of Oahu and another 18 people on west shores as a rising swell brought advisory level surf to south shores of all islands.

The National Weather Service issued a high surf advisory until 6 a.m. Monday.

Surf was expected to reach 8 to 12 feet on south shores by Sunday. West shores could see 4- to 7-foot surf through Sunday.

The rescues on Oahu included a woman in her 20s who swallowed water at Ala Moana Beach Park and had to be helped out of the surf. She didn’t require hospitalization. Lifeguards also rescued someone at China Walls in Hawaii Kai and 3 people from a surf spot called “Puka Pants” near Hakimo Road and Farrington Highway in Nanakuli.

Lifeguards also responded to the Blow Hole for a rescue Saturday evening.

Ocean Safety also reported issuing 1,000 warnings on the south shore and 2,000 preventative actions on west shores.

Weather forecasters expect waves to drop below advisory-level but remain high Monday and Tuesday as the swell gradually declines.