Emergency teams were able to retrieve the boy at South West Rocks, about 400 kilometres north of Sydney, but he died at the scene.
Earlier on Sunday, a helicopter spotted a father and son floating in the water near Wattamolla Beach, south of Sydney. The 14-year-old son was resuscitated, but the father was later pronounced dead.
Meanwhile, Police in Victoria are continuing to search for a 41-year-old man who went missing near San Remo on Friday.
Surf Life Saving New South Wales said it has carried out more than 150 rescues since Good Friday.
Mr Pearce said a “perfect combination” of high temperatures, the holiday weekend, and dangerous ocean swells across much of New South Wales and Victoria caused the spike in deaths.
Although conditions are set to improve on Monday, authorities urged those visiting the coastline to exercise caution.
Australian prime minister Anthony Albanese expressed sympathy to the victims’ families. “Please, everyone, be careful. Families in particular, be careful of your kids,” he said.
According to Royal Life Saving Australia, 323 people drowned across the country in the year to June 2024.
That figure includes those who died in rivers and creeks, as well as at beaches. Nearly 40% of the deaths were recorded in New South Wales.