Swimmers at a public pool in north-west Queensland got a weekend surprise when they found they were sharing the water with a family of baby freshwater crocodiles.

The unusual swim squad was found by a man doing laps just after the Mt Isa pool opened on Sunday.

The man then alerted the pool's manager Brian Rodriquez.

"He said 'Brian I don't mean to alarm you but I think there's a crocodile in the pool'," Mr Rodriquez said.

"We got everyone out of the water and we ended up finding five baby crocs swimming around.

"Then we found another two wandering around on the concrete after that as well."

It is believed pranksters released the reptiles into the pool area early Sunday morning.

On Sunday evening another two crocodiles were found in the complex, taking the total to nine.

Mr Rodriquez was tasked with catching them.

He admits he did wonder whether their parents might be nearby.

"They're probably between 25 and 30 centimetres, so they're not huge - probably a ruler length," he said.

"But when there became more and more I thought wow - has someone played a prank or is their mummy around, or daddy around?'

"From what I can see they all seem to be okay and healthy.

"We took our turtles out of our tank that we have here at the pool and we put them in the water there for them to be a little bit nicer than ... the chlorinated water that they've been swimming around in."

Unfortunately, one of the nine baby crocodiles found in the pool died overnight after spending Sunday in the sun.

"He was right at the deep end of the pool so he had obviously travelled a fair way from where they were put into the pool," he said.

"When Brian picked him up he was looking very pale, his skin was white and he was quite lethargic.

"But then when we came down again this morning he'd gone to crocodile heaven."

The other eight crocodiles will be released back into the wild by a local ranger tonight.

CCTV footage reviewed in hunt for clues

After being caught the baby crocodiles were kept in a tank that normally houses turtles ( Supplied: Brian Rodriquez )

The pool managers are reviewing CCTV footage to see if they can find out how the crocs came to be swimming laps in their pool.

Mr Rodriquez already has some theories of his own.

"My guess would be that somebody's just jumped the fence or chucked them in the pool and they've found their way to the water," he said.

"Judging by their size - they'll be a few weeks old - so maybe someone's picked them up, probably from the lake, and taken them home.

"Then they've either dumped them here to be funny, or they weren't sure what to do with them now being that little bit bigger."

Ironically, it is not the first crocodile encounter at the Mt Isa aquatic centre.

Three years ago a one-and-a-half metre crocodile was found on the grass next to the 50-metre pool.

It is still not clear how that animal came to be inside the pool grounds.