Large waves on Oahu’s north and west shores kept lifeguards busy with 15 rescues on the North Shore and two rescues and 41 assists along the Leeward Coast today, according to the city’s Ocean Safety Division.

Lifeguards also took 4,155 preventive actions on both shores to keep people out of the water.

An 11-year-old girl was treated by lifeguards and paramedics after swallowing water at Nanakuli Beach Park and was taken to a hospital, Emergency Services spokeswoman Shayne Enright said. She was the only rescued person taken to a hospital.

A high surf warning issued by the National Weather Service continues to be in effect through 6 p.m. Monday. The warning covers northern and western shores of Niihau, Kauai, Oahu and Molokai, and the northern shores of Maui.

Forecasters have also issued a high surf advisory for the western shores of Hawaii island.

The weather service said the northwest swell grew today, peaking with waves up to 30 feet high for the smaller islands. On the leeward side of Hawaii island, waves were expected to peak at about 20 feet tonight.

Monday the waves will bring hazardous conditions, including rip currents and coastal flooding, officials warn. Beach erosion is also possible, especially during high tide early in the morning.

A small craft advisory also remains in effect until 6 p.m. Monday, with westerly winds of 17 mph veering north in the afternoon. The channels will see a northwest swell of 13 feet, building to 14 feet tonight, with isolated showers.

Northeasterly winds of 23 mph due tonight will add another 8 feet to the wave heights, forecasters said. The wind speed is expected to increase to 29 mph Tuesday.