"It is definitely the season of distractions — the knock at the door, the ringing phone, other children crying out for assistance; they are the things that take our attention away from backyard swimming pools."

Key points: Highest drowning death toll for NSW over the festive season

Highest drowning death toll for NSW over the festive season More deaths occurred in inland waterways than on the coast

More deaths occurred in inland waterways than on the coast Hot weather means many more people in the water than usual

Michael Ilinsky, a spokesman for the Royal Life Saving New South Wales, is addressing the current spike in holiday drownings.

It has been a disastrous start to summer, with 15 people dying in drowning incidents since Christmas Day, three of them toddlers and one a teenage boy.

The unusually high number of deaths has highlighted the greater danger water poses during the holidays, Mr Ilinsky said.

He said all beaches, pools and rivers posed risks to swimmers, especially children.

So, what are the factors that lead to drownings and how can people stay safe this summer?

Is the number of deaths unusual?

Yes, it is an unusually high death toll for the season.

Surf Life Saving NSW spokesman Liam Howitt said there had been a variety of factors contributing to the spike in drownings.

"It certainly has been the highest [death toll] we have seen over the festive season," Mr Howitt said.

"That spike is not just in the surf, but in backyard pools, and inland rivers and lakes.

"Obviously it's the festive season, as well, so people do things like having a drink to celebrate during that time, and that can potentially cause people to make bad decisions around the water."

Map NSW drownings over Christmas 2016

Is the NSW heatwave a factor?

Mr Howitt said it had been an exceptionally hot start to summer across the state.

The heatwave meant that many more people who weren't necessarily strong swimmers were getting in the water.

"What our volunteers — our lifesavers — are telling us is that it has been an exceptionally busy period over the summer; there are certainly more people travelling to the beach," Mr Howitt said.

"It is certainly hotter than this time last year."

What conditions should people avoid?

Mr Howitt said awareness about conditions was extremely important for swimmers getting in the water.

"It is really knowing about what your environment is like before you enter the water," Mr Howitt said.

"This is the same regardless of what water you are entering into — whether it be the surf, the river, the pool, always check before you swim."

Inland waterways are actually the leading fatal locale for drownings in NSW, and Australia, according to the Royal Life Saving annual report.

Seventy-five people died from inland waterway accidents between July 2015 and June 2016, with 63 dying as a result of a beach swim during that same period.

When is it safe to swim in the ocean?

There is no absolute way to stay safe while swimming at unpredictable beaches.

"We can see how quickly things can happen," Mr Howitt said.

"The ocean is a dynamic environment, with people getting caught in rip currents."

People are encouraged to swim between surf lifesaving red-and-yellow flags.

"Also just knowing your ability as a swimmer is critical: if you are not confident, it is doubly important you swim during the daylight hours, between the flags," Mr Howitt said.

How dangerous are rivers and lakes?

The scene of a search for a man who disappeared in the Murrumbidgee River at Wagga Wagga. ( ABC Riverina: Simon Wallace )

"Inland waterways are our most lethal environments when it comes to drowning," said Mr Ilinsky, from Royal Life Saving NSW.

"Our rivers, lakes and dams claim more lives than beaches, so we are seeing again a number of incidents across summer where people have gone into these environments, which are often colder, deep, and have muddy banks, crumbling banks, and even people not wearing life jackets when they're on boats.

"If swimming skills are poor or supervision is lacking, stay out of the water."

A major factor for the inland river and lake deaths was that very few inland waterways were patrolled with lifeguards.

A Royal Life Saving guide lists the main factors that lead to death, including lack of lifeguards, panicking when getting caught on submerged objects, and hard-to-read currents:

"The flat, still surface of an inland waterway can give a false sense of security. Currents, even in seemingly tranquil waterways, can prove dangerous."

The guide tells swimmers to enter the water slowly to avoid injury from unseen objects and to test currents, and to be aware that conditions can change quickly.

They should also be aware that the water could be deeper or shallower than appears on the surface, it says.

A warning to parents around pools

Mark Lever from the Careflight rescue service said while everyone needed to take extra care with backyard pools, parents had a responsibility to always supervise their children.

"Well, they call it the silent killer, with good reason: In every single instance you will hear that nobody heard a thing, the child seems to have disappeared, they were out of sight for moments."

New South Wales Fair Trading has fence guidelines available for pool owners, which should be strictly followed to help keep children safe.

The three toddlers who have died since Christmas were all in backyard pools, and police have said in those cases the pools met all safety requirements.

Why are so many males drowning?

Males make up 90 per cent of coastal drowning deaths in Australia.

"It is very difficult to quantify why young men are so at risk," Mr Howitt said.

"Over-confidence could be a factor, along with risk-taking behaviour."

Are tourists at greater risk than locals?

A 27-year-old Pakistani national died while swimming with friends at the Mermaid Pools, south-west of Sydney. ( ABC News )

Mr Howitt said there was not enough research yet into the current spate of drownings about who was most at risk, including when it came to whether they were locals or tourists.

"It is not only tourists who get into rips, it is also locals who have lived on the coast," he said.

"Other risk factors include those not so experienced on the coast, particularly those who move from different communities to coastal communities."

Lifesavers have been working with at-risk groups, including young people from western Sydney, he said.

"The overall research has highlighted the most at-risk group is males aged 15 to 29.

"Through the schools, we try and reach the most at-risk communities before they reach that age group."