More than 230 people have been rescued off Victoria's beaches since the start of the summer lifeguard patrol season, with more than half of those brought to shore since Christmas Day.
The high number of rescues has prompted urgent warnings from Life Saving Victoria, after lifeguards and lifesavers rescued 21 beachgoers on Friday.
A father and his young son were pulled from waters at Venus Bay at South Gippsland, with the boy later flown to the Royal Children's Hospital for treatment.
The beach was shut down while lifeguards responded to incidents.
Within an hour, another three people at an unpatrolled beach a couple of kilometres away had to be rescued by paramedics along with lifeguards.
That incident was particularly concerning given the three were close to where lifeguards were patrolling, Life Saving Victoria state agency commander Kane Treloar said.
"Statistics show that you're almost 68 per cent more times more likely to drown on a public holiday," he told reporters on Saturday.
"With the behaviour that we've seen from some people over the last couple of days, that leaves us concerned, so we're urging everyone to make good decisions around the water."
Since July this year, 22 people have drowned in Victoria. Four people have drowned since Christmas Day.
Rip currents were taking shape "all over the place", including in Port Phillip Bay, and were an ever-present danger on beaches, Mr Treloar said.
He urged people to avoid drinking and swimming in the New Year, to swim in patrolled areas or pools, and supervise children whenever they were in the water.
"We've seen horror numbers over the past couple of summers where ... people have lost their lives, and we're certainly doing everything we can to make sure that we're going to keep the number as low as possible this summer," Mr Treloar said.
"Both of the holidays all fall on the weekend this year, and the weather is going to be nice, so all of those risk factors together have got all of our lifesavers and lifeguards on high alert."
Melbourne was expected to hit 29 degrees on Saturday, 34 degrees on Sunday, and 32 degrees on Monday.
