A large south-southwest swell kept Oahu lifeguards busy for a second consecutive day.

According to Ocean Safety officials, lifeguards executed 57 rescues and 745 preventive actions as of 4 p.m. on Monday as wave heights reached 12 feet along the south shore.

Ocean Safety officials had arranged for additional rescue watercraft to be on hand in anticipation of increased activity.

An Ocean Safety report affirmed that most of Monday’s rescues were indeed conducted using rescue watercraft.

The department had earlier warned ocean users to be aware of the heightened danger and not to test their capabilities in the potentially treacherous conditions.

However, the lure of big surf in town proved powerful for hundreds of surfers, bodyboarders and other beachgoers on Monday.

Lifeguards reported incidences of broken boards and leashes and assisted surfers who found conditions too challenging for their abilities.

The swell, which arrived late Saturday and was initially forecast to diminish by Monday, is the result of a powerful low-pressure system in the South Pacific.

On Sunday, lifeguards conducted 17 rescues and nearly 600 preventive actions.

A high surf advisory remains in effect for the south shores of all islands until 6 p.m. Tuesday.

The public is advised to remain mindful of strong breaking waves, shore break and strong longshore and rip currents that could make swimming difficult and dangerous.

Surf along south shores is expected to drop to 6 feet to 10 feet and gradually diminish by midweek, when a smaller south swell is expected to arrive.

A long-period east swell generated by Hurricane Andres in the east Pacific, is also expected by midweek and surf along east shores may build to advisory levels by the weekend.

In addition, a moderate northwest swell is possible beginning Friday night, which could continue through the weekend.