A man who died scuba-diving at Catherine Hill Bay on Sunday was among three fatalities inside 72 hours on the NSW coast.
The 55-year-old, who was diving with his 16-year-old son south of Catherine Hill Bay jetty, is understood to have suffered a medical episode in the water.
Paramedics were called to the scene about 11am and, along with lifesavers, administered CPR and a defibrillator, but the man could not be revived.
He had been dragged from the water unresponsive by his teenage son.
Surf Life Saving NSW chief executive Steven Pearce said on Monday the incident was part of a "pretty ordinary" and "tragic" long weekend.
"We've been kept on our toes all weekend," he said.
"We had two drownings within the space of an hour [on Sunday]. One at Catherine Hill Bay that involved a scuba diver and another one an hour later up at Urunga.
"That was a really tragic incident involving a family visiting from Wollongong where a father and son were swept out in a river mouth in a rip and the father couldn't remain treading water."
Mr Pearce said a similar incident occurred on the South Coast on Friday.
"A father went in to save his children and he perished, and his children were able to be rescued," he said.
The Urunga and South Coast fatalities occurred at unpatrolled locations, which Mr Pearce said was disappointing after last season's safety message of: "If we can't see you, we can't save you."
"Last year we had, I think, 44 coastal drownings right across NSW and that was the second highest year on record," he said.
"Majority of those were outside of patrolled locations.
"The key takeaway is, particularly coming into the festive period and people visiting new locations, if [people are] unsure of the location - they should be swimming at a patrolled location where there are lifeguards or lifesavers on duty, and red and yellow flags flying."
Mr Pearce issued a call to arms for Hunter residents to use "local knowledge" to warn those who may not be aware of dangerous waters.
"It's going to be a real hot spot for tourists [on the Hunter coast]," he said.
"If there's something we would ask it's for locals, if they did see any of the visitors going into waterways or water courses where they know it's dangerous from local knowledge, that they intervene and warn those people of the dangers.
"We'd ask people to be great community members and advise any of the visitors of the dangers ... and if they did see someone get into trouble, that they rang triple zero ... or if there were lifeguards or lifesavers on duty, notify them straight away."
Hunter beachgoers should also think twice about swimming near, but not in, flagged areas.
"The majority of drownings occur within 600 metres of a patrolled location," Mr Pearce said.
"That's people coming to the beach and thinking, 'aw look, it's a bit calmer down that end of the beach we might go down there'.
"But predominately, it's calmer because there's either a big deep hole or a large rip that's running, and the rip makes makes it look nice and calm.
"That's where people are really fooled."