Crocodiles have "very powerful tails" that enable the animals to push themselves out of the water, said expert Adam Britton.
The 10-year-old girl was bitten on both feet by a mulga snake, also known as a king brown, estimated to be more than three feet in length by a local snake catcher.
Brian Ahrens from the town of Humpty Doo had to fight off the predator to catch a barramundi.
NT Police Watch Commander Siiri Tennosaar described the 23-year-old as the "luckiest man alive" after he escaped the encounter without life-threatening injuries.
"I just ripped him out of the bassinet and took him in and put him on his change table…turned the lights on and there were maybe three or four bites to his cheek," said mother Julia McLennan.
Jamie Hall said the shark bite occurred at a spot known as Nightcliff Jetty while he was fishing with friends on Saturday afternoon.
"I was like, What the hell is that?" Tee Hokin, the angler who caught the creature, said.
Deaths from sea-snake bites are rare.
It's roughly the same length as the average family car.
The 11-foot reptile was found near the man's body.
The man was taken into remote waters off the coast of Western Australia.