At least five people were injured when four large waves slammed into a tour catamaran sailing near Kewalo Basin Harbor today.

Honolulu Emergency Medical Services reported that more than 30 people were aboard the vessel when the incident occurred around 11 a.m. Paramedics transported one passenger in serious condition and two with minor injuries from the harbor to a nearby trauma facility. Two other passengers declined treatment.

A spokesperson for Na Hoku II, which operates the Na Hoku III catamaran that was involved in the incident, declined to comment.

The National Weather Service issued a high surf advisory for the south-facing shores of all islands in effect until 6 a.m. Monday, with surf of 8 to 12 feet and strong breaking waves and currents making swimming dangerous.