An Australian teenager suffered serious injuries to his arm when he was attacked by a crocodile after jumping into a river infested by the reptiles for a dare.

Paramedics said he was lucky to escape with his life in the incident, which emerged as the authorities recovered the body of another man who also may have been attacked by a crocodile in nearby waters.

British packpacker Sophie Paterson told how Lee de Paauw had started bragging that he could swim in the river, a known habitat for aggressive saltwater crocodiles.

They were at a hostel in the northern Queensland town of Innisfail around 2.30am local time on Sunday.

Ms Paterson said she and several others egged him on, though none of them thought he would actually get in the water.

But he did get in the water, and seconds later, a crocodile latched onto him.

"It all happened very fast. Pretty much as soon as he jumped in, there was splashing and screaming," Ms Paterson told Queensland's Courier-Mail newspaper.

"There was blood everywhere and he just wouldn't stop screaming."

Mr de Paauw, from Queensland state, managed to pull himself out of the water.

Queensland paramedic Neil Noble said the teenager suffered extensive injuries to his arm, and was lucky to escape from the crocodile before the animal drowned him.

Meanwhile, Queensland authorities on Monday recovered a body believed to be that of a man who vanished on Saturday while spearfishing alone in waters just north of Innisfail.

The 35-year-old man's boat was found anchored off Palmer Point, about 30 miles north of Innisfail, on Saturday evening, with his spear gun floating in the water nearby.

An air and sea search was launched and officials spotted a body in the water on Monday morning, Queensland police said.

An initial investigation suggests the man may have been taken by a crocodile, police said.

Wildlife officers were hunting for the animal, believed to be around 13 feet long.

Crocodiles have been a protected species in Australia since the 1970s, which has led to an explosion in their population across the country's tropical north.

Because saltwater crocodiles can live up 70 years and grow throughout their lives - reaching up to 23 feet in length - the proportion of large crocodiles is also rising.