Social media and radio talkback was awash on Monday with members of the public vowing never to swim in the sea again after 16-year-old Sam Kanizay​ emerged from a dip at Brighton beach on Saturday night with his lower legs covered in blood and tiny bite marks.  

Sam, who had  continued to bleed so profusely from the pinprick-size holes in his legs, that his father rushed him to hospital, where his bizarre case puzzled doctors. He was still in hospital on Monday night.

St Kilda Football Club told its players to avoid bathing at Brighton beach after the incident.

Saints midfielder Koby Stevens joked that "I've still got my feet today" because "the whole group got the message of the young bloke who nearly had his feet eaten off down at the beach."

On Monday afternoon, Museums Victoria helped shed light on the incident.

It confirmed [the queasy can stop reading this sentence now] that, yes, tiny flesh-eating creatures were probably behind the attack.

Museum marine scientist Dr Genefor​ Walker-Smith has examined specimens collected by Sam's father, Jarrod Kanizay – using bites of meat as lures – at Brighton on Sunday night, and said the creatures were sea fleas, not sea lice as first thought.  

Yes, these tiny (half-a-centimetre to one-centimetre long) carnivores will feed on human flesh, but Dr Walker-Smith said there was no cause for alarm.  

She said the number of bites sustained by 16-year-old Sam was unusual and a swarm of fleas might have been attracted by a cut in his skin, or Sam might have stepped near a fish carcass they were feeding on. 

Sea fleas are scavenging amphipod crustaceans belonging to the lysianassid group. The bad news is that they're found all over Port Phillip Bay and all over the world in hundreds of species. 

"They're there all the time; you could put a piece of meat in the water, anywhere in the bay, and you could find them," Dr Walker-Smith said.

But she wouldn't recommend closing the beach, and said people shouldn't stop swimming there.

"I think this is quite a rare thing. I really just think [Sam] was in the wrong place at the wrong time, probably."

Dr Walker-Smith would be happy to swim at Brighton beach herself but suggested that swimmers watch out for dead fish lying around and be "careful where you put your feet".

She said it was not surprising that Sam's bleeding would not stop – this symptom had been seen in bite cases from crustaceans before, although she hadn't heard of it among crustaceans in this group.

"It is possible that the amphipod has an anti-coagulant that it released like leeches do, so it stops the blood from clotting."  

Dr Walker-Smith said sea fleas inhabited colder and warmer water, and were more active at night, to avoid fish predators .

"It probably did make it worse that [Sam] was standing still; they may not have been able to cling on too tightly if he had been moving through the water. They're used to eating dead things still on the bottom [the ocean floor]." 

In response to some of the more out-there social media comments, she had "no idea" if the attack was related to the full moon and said it wasn't related to bans on fishing in Port Phillip Bay. 

She planned to keep some of the Brighton sea fleas pickled in alcohol and invite Sam in future to "have a closer look at them under the microscope".

"We'll keep them as a record of this event and try and identify them down to a species, which will take a little bit of time."

Paul Duckett, a daily swimmer with the Brighton Icebergers since 2001, said what had happened to Sam was bizarre and locals had asked his group whether they would still swim on Monday.

But the dozen or so winter regulars had "shrugged it off" and swam straight out as normal from Dendy Street beach. "We're probably too gritty and tough and old for those creatures to worry about," he said.

"We swim there every day and we're in the water for anything from 15 to 30 minutes, and no one's ever experienced anything like this," he said.

A Department of Environment, Land, Water and Planning spokesman said sea fleas were a "common and natural part of a healthy marine ecosystem" that "keep our marine waters clean by consuming dead and dying marine animals".

"DELWP advises swimmers to wear a wetsuit with boots to reduce the risk of being exposed to sea fleas and avoid swimming at night. "