Drownings in Australia are up 51% compared with the same time last year, after five men drowned on New Year’s Day.

Preliminary figures compiled by Royal Life Saving Australia show that 47 people drowned from 1 December to 1 January, compared with 31 last summer.

The number of people who drowned at beaches or in the ocean has reached 21, higher than the 14-year average for December of 13 drowning in coastal waterways but below last year’s toll of 23.

The majority of the deaths have been in Victoria, where a 45-year old Bairnsdale man drowned while swimming with his wife and family at Paynesville, just 15 minutes from his hometown on the Gippsland Lakes, at 4.50pm on Tuesday.

About an hour-and-a-half earlier, a 66-year-old man was pulled from the water at the northern Tasmanian resort town of Hawley Beach.

In both cases paramedics and members of the public attempted to revive the men, but were unsuccessful.

Earlier that afternoon a 35-year-old man drowned off Clovelly Beach in Sydney, and a man in his 40s died after being rescued from the surf at Frenchman’s Beach on North Stradbroke Island in Queensland.

A fifth man, aged in his 20s, drowned while free diving along the Rockingham wreck trail, which has been set up for divers just south of Perth, about 12pm Western Australian time.

All five deaths will be subject to coronial investigations.

The Royal Life Saving Australia national operations manager, Craig Roberts, said heatwaves and unusually hot weather, which is forecast to be repeated across much of Australia on Friday, had drawn more people to both inland and coastal waterways, as well as backyard pools, to escape the heat.

Roberts said an analysis of the last 10 years of drownings showed that a number of those who died were people, particularly men, who were familiar with the area where they were swimming but overestimated both their knowledge and their fitness. He said that trend had continued this summer.

“We have seen a large number of adult males who have drowned not only this summer, but over the last five or six years at an increasing rate, and that’s largely due to a number of people going into the water without realising they are not as fit as they used to be,” he said.

While 27% of those who drowned in Australia in the past 10 years were born overseas, more than half of those people had lived in Australia for a decade or more.

Roberts said people drowning while trying to rescue a friend or loved one was also a significant risk, and urged people, particularly parents, to take first aid and surf life-saving courses so they are able to help if their children get into trouble. In 76% of cases where someone has attempted a rescue, he said, the rescuer drowned while the other person survived.

“It’s a tough decision but if you are going to go into the water [to attempt a rescue] please make sure that you have the skills to do so,” he said.

Shane Dawe, the national coastal risk and safety manager for Surf Life Saving Australia, encouraged people to seek out a patrolled beach even if it meant driving a bit further or enduring larger crowds.

“It only takes a moment for you to get into danger, and it can happen to the best people,” he said.

Dawe said beachgoers could check the local conditions, including the location of rips, on Beachsafe.org.au.