Rio de Janeiro's waterways are about as clean as a dirty toilet bowl—raw sewage literally flows into them every day. So in preparation for the 2016 Summer Olympics, US rowers, sailors, and swimmers are getting creative to protect themselves against pathogens lurking in the water.

The latest measure? The US Olympic Rowing Team revealed earlier this week that they will wear a newly-developed unisuit complete with an "antimicrobial finish" while they train in Rio's Rodrigo de Freitas Lagoon, where recent Associated Press investigations have found virus counts thousands of times higher than federal safety limits.

But health experts aren't sure antimicrobial gear will do much to protect water athletes from nasty viruses and bacteria. "They will literally be immersing themselves in very high levels of pathogens," says Katherine Mena, who researches waterborne pathogens at the UT-Houston School of Public Health. "The infection risk will be pretty high."

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Mena was one of the water quality experts who helped analyze data collected by the AP during its investigation of Rio's water. Last summer, the news organization found unsafe levels of fecal bacteria, enteroviruses, rotaviruses, and adenoviruses in every water sport venue. Those can cause diarrhea, vomiting, and respiratory symptoms—not exactly what you want to wake up to the morning of the biggest race of your life.

Athletes have already been strategizing to protect themselves. Some will try to build up immunity by arriving early, while others plan to avoid the water until just before competition in the hopes that the symptoms won't kick in until after the Games are over (the incubation period for viruses can last up to 10 days). The US rowing team will set up hand-washing stations for rowers when they leave the water. "We are open to any steps we can take to help mitigate the polluted water," says Liz Soutter, the team's assistant program manager.

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That includes the teams' spiffy new apparel, released by the company Boathouse Sports. Textile engineer Mark Sunderland wove synthetic fibers into seamless garments that wick away moisture from the athlete's skin. That basic layer of protection could offer some protection against bacteria and enteric viruses (the kind that give you gastro), which can enter through the skin and open wounds. But the unisuit still leaves most of the athletes' limbs exposed.

The suits do have a second layer of protection: a chemical-based antimicrobial finish. Biocides like metal, salt, halamine, or phenolic compound kill or inhibit some microorganisms when they touch the surface of a garment. But they won't necessarily prevent infection. "Not all biocides can kill microbes fast enough," says Gang Sun, who researches textile and clothing technology at UC Davis. Often the killer molecules don't release from the fabric fast enough to meet the onslaught of microbes, or are plugged up by initial layers of dead bacteria cells.

And most of these biocides aren't very good at attacking viruses—the largest threat to rowers. As oars hit the water, virus-filled water droplets aerosolize, waiting to be inhaled by heavily-breathing rowers. Water spray only needs to contain a couple of particles of a virus to infect a rower through an eye or a gaping mouth. How do you stop that from happening? "They would basically have to put a mask over their face," says Valerie Harwood, a water quality microbiologist at the University of South Florida. Not likely to optimize the athletes' VO 2 max.

In the end, the best line of defense for rowers and other water athletes might be inside their bodies. Olympians' immune systems are some of the best in the world, and they'll probably be able to fend off most of the viral and bacterial infections their bodies encounter. "These are organisms that they are exposed to everyday," says Mena. But, she adds, not where exposure is so high. While Rio's murky waters (not to mention Zika) might scare off the faint of heart, the US Rowing team is ready to take on the germs. Not one member has withdrawn from the Games.