A young crocodile has been returned to a mobile wildlife zoo after being found sunning itself on a riverbank in Sydney's south by a family on an Easter Sunday stroll.

It was one of two young crocodiles, named Snap and Crackle, stolen from the Get Wild Animal Experiences mobile zoo in early March.

Aaron Hughes, who lives near Salt Pan Creek on the Georges River, said he did "a double take" when he spotted the reptile on the mud flats while walking with his wife and young son.

He said he had heard about the missing crocodiles on the news when they went missing.

"There had been a bit of a running joke among the street and with my friends that those crocs are going to be turning up in a few years being 2 metres and 3 metres long, so we sort of realised straight away where it was from," he said.

He said there had been some sightings in the Georges River since they had gone missing from the park, which is a couple of suburbs away from where the Hughes family lives at Peakhurst.

Mr Hughes said he was very nervous about what to do with the crocodile.

'I just picked it up and walked it to the house'

"Both my wife and I looked at each other and were having a bit of a laugh about what to do next, but we were mainly concerned for the animal's welfare," he said.

"Basically it did look a bit malnourished and we weren't sure what to do.

"As we've all done, we've seen Steve Irwin the crocodile hunter and we were well versed in maybe coming up behind it and grabbing it as it wasn't moving too quickly.

"I'm a fisherman at heart and I do like to sometimes say that my catch is a little bigger than what is real, but it was quite small so really I could just walk up on it and it didn't really move at all and I was able to pin it behind the neck.

"Didn't need to sit on it or anything like that, just picked it up and walked it up to the house."

Crocodile finder Aaron Hughes kept the reptile in the bath until police collected it. ( Supplied: Aaron Hughes )

Mr Hughes called a vet for advice and then rang Kogarah police who came and took the animal back to the station for safe-keeping before the zoo owners were able to collect it.

The owners had put out several appeals for people to keep an eye out for Snap and Crackle, as they were not expected to survive long in the wild in the cooler Sydney waterways.

Mr Hughes is convinced that Crackle is the one still at large.

"Their names are Snap and Crackle which I thought were pretty funny names and we think we managed to get hold of Snap because he did have a few goes when we were bringing him up to put him in the bath."

Inspector Leonard James from Kogarah Local Area Command is hopeful the remaining missing croc will soon be found.

"I can't say I've seen a crocodile wandering the creek at Peakhurst and hopefully we never will again," he said.

"Crocodiles are a dangerous beast and can kill, although this one was only 80 centimetres in length.

"The best thing to do is to notify police and we will do our best to make sure it's captured and returned to its rightful residence.

"If anyone has any information in relation to that they can contact Sutherland police or Crime Stoppers."