Dunking around in the sea can feel like a rebirth: you emerge virtuous, salty, and oblivious to your existential angst for five beautiful minutes at least.
But people who swim, "bathe" or play water sports in the sea are substantially more likely to get stomach bugs, ear aches and other infections than those who don't, according to a large-scale research analysis by the University of Exeter Medical School.
The analysis found that swimming in the sea doubled the odds of reporting "general ear ailments", with the odds of reporting an earache specifically rising by 77 percent. For gastrointestinal illnesses, the odds increased by 29 percent. Not putting your head under makes no difference, either.
Going by strict inclusion criteria such as scale, researchers drew data from 19 out of a potential 6,919 studies. The studies looked at the links between sea bathing and the incidence of illness in countries including Australia, New Zealand, the US, Denmark, and Norway.
Australia's coasts are subject to rubbish, sewage, industrial waste, storm water and dredging. According to a 2013 study, each square kilometre of our sea surface is contaminated by around 4,000 pieces of "tiny plastics", which are all "loaded with pollutants".
People tend to assume developed nations have cleaner seas, writes Dr Anne Leonard of the University of Exeter Medical School. However, "We think this [data analysis] indicates that pollution is still an issue affecting swimmers in some of the world's richest countries."
Dr Will Gaze, who supervised the research, said: “We don’t want to deter people from going into the sea, which has many health benefits ... However, it is important that people are aware of the risks so they can make informed decisions."
Most people will recover from infections without medical treatment, Gaze added, but they can be more dangerous when contracted by vulnerable people like the very old or young, or people with pre-existing health conditions. "We have come a long way in terms of cleaning up our waters, but our evidence shows there is still work to be done," he said.
This article originally appeared on VICE AU.