Portuguese man-of-war floats ominously off Rio. Photo: Courtesy of ©Daniel Botelho

Contaminated water off Rio de Janeiro might be only one concern for beach-going tourists and water-sports athletes at the 2016 Olympic Games, which begin this week in Brazil.

Another possible threat is posed by dangerous sea creatures that swept in with the currents last week.

Daniel Botelho, a renowned nature photographer who lives in Rio, told GrindTV that several swimmers were stung by Portuguese man-of-wars last week off Barra da Tijuca, site of the Olympic Training Center and about 15 miles from water-based competition venues.


Dangerous sea creatures sting several swimmers not far from Olympic sports venues. Photo: Courtesy of ©Daniel Botelho

The photographer captured three beautiful images of one colorful man-of-war, with Rio as a backdrop, before painful stings drove him from the water. (Stings typically leave welts that can last for days.)

"I made one photo, two photos and bang! It felt like hot iron on my skin,” Botelho said. “But I kept shooting until as many tentacles as I could stand got me. After making sure I got a few images, I decided to leave the water. It took about 12 hours for the pain go away, and some fever happened, and then an unpleasant itching."

Botelho, whose sister-in-law also was stung, said swimmers were warned about the presence of man-of-wars, but beaches were not closed.

The Portuguese man-of-war is not a jellyfish, despite its appearance. It's a siphonophore, consisting of may organisms called polyps. Its name is derived from its uppermost polyp, a purplish bladder often visible above the surface, that resembles a warship under sail.


Third Portuguese man-of-war image captured before photographer is driven out of the water by stings. Photo: Courtesy of ©Daniel Botelho.

Tentacles can extend more than 150 feet, and are capable of stinging even after breaking free and drifting on their own, or washing ashore. Man-of-war stings are not deadly, but pain associated with stings is usually intense.

Botelho, who travels the world photographing sharks and other marine creatures, had just returned from a lengthy expedition and was relaxing at the beach with family.

RELATED: Stunning image illustrates urban shark phenomenon at Recife, Brazil

"I was in the water with my brother and his wife when suddenly she started to scream, ‘Something is biting me. Help me please!' " Botelho recalled.

His brother swam to the rescue while Botelho, realizing that a rare photo opportunity had presented itself, rushed home to collect his camera.Once back in the water, he found himself surrounded by several man-of-wars moving swiftly with the wind.

"My hands were shaking and my heart was speeding up, but not because I was afraid of the sting," Botelho said. "I was terrified with the possibility of missing the unique opportunity to make an underwater image in front of my house, including my house as part of the background – maybe a once-in-a-lifetime opportunity."

He told GrindTV on Monday that man-of-war encounters in Rio's waters are rare, and that an easterly wind might have carried the stinging creatures farther offshore. He added, however, that another wind change could bring the dangerous sea creatures back again.

More from GrindTV

A complete guide to car camping on the cheap

Why dawn patrol's got nothing on heading down at dusk

The case for not traveling with a surfboard