The Dangers of Surfing After a Rain

Photo by Paul Fisher

Is the 72-hour rule still the foremost guideline for avoiding sickness?

By Dashel Pierson/ Surfline

To surf, or not to surf. That’s the question many of us frequently face, when a deluge falls from above, surface streets are lined with tributaries, and bacterial runoff rushes towards the ocean. But, there’s waves – and the little surf demon inside our brain prods us to paddle out, drowning out the angel of better judgement.

As California continues to experience an exceptionally wet winter, Golden State surfers have been confronted with the post-rain surf conundrum more often than usual. Luckily, the Surfrider Foundation just completed a three-year study exploring the dangers of surfing during or after a rain. The report examined 654 surfers over 10,081 sessions in San Diego from the winter seasons of 2013-14 and 2014-15.

And, surprise! The study found that surfing during or after wet weather exposes the body to higher chances of gastrointestinal illness (GI), i.e. pesky bacteria capable of causing cramps, nausea, vomiting, and diarrhea. But, by how much exactly? The study reads:

“When surfers enter the water during or in the 72 hours following storm events, an average of 30 per 1,000 will contract GI illness, compared to 18 per 1,000 surfers who will contract GI illness without entering the water, and 25 per 1,000 who will contract GI illness when entering the water during dry weather. From a health risk perspective, that is an extra – or excess – risk of 12 surfers per 1,000 on average who will become ill when they enter the ocean in wet weather, compared to when they do not enter the ocean.”

In other words, on average, there is a 3% chance of contracting an illness if you go surfing during or within 72 hours after wet weather. In addition of gastrointestinal illness, the study explored other disorders including rashes and ear infections, finding that an increased 19 per 1,000 surfers (1.9%) were susceptible.

And the age-old “72-hour rule” was once again confirmed by the study, meaning water levels typically return to what’s considered safe three days after a rain. The study says: “Illness rates were highest when surfing during rain and the first day after the rain. Illness rates decreased with each day following rain, declining to near baseline levels after 3 days.”

The study also found, unsurprisingly, that surf spots with high runoff levels – locations with elevated fecal indicator bacteria (FIB) – amplified the threat of infection. At the locations where testing took place, Tourmaline Surf Park in Pacific Beach and the north end of Ocean Beach, the FIB readings decreased as the researchers moved further away from runoff areas.

So – a 3% chance of infection from surfing during wet weather. And a 2.5% chance if surfing during dry weather. But even if you didn’t go in the water after a rain, you’d still have a 1.8% chance of contracting a gastrointestinal illness. (Considering, of course, any number of outside factors that could sway the data). You might be thinking – those numbers don’t seem too bad, huh? Maybe slimmer than you imagined. That is, until you become a statistic and start growing a sixth toe.