It might seem like the 84 beach-goers who got stung by jellyfish on Friday the 13th just had bad luck.

But it was enough bad luck that Oahu’s best-known snorkeling location, Hanauma Bay, was closed Friday. Conditions will be re-evaluated to see if it will be reopened Saturday, the city said.

Eighty of those people were stung at Hanauma Bay, and another four in Kailua before 11 a.m. Friday. There were approximately 200 box jellyfish sighted at the two beaches.

Hanauma Bay was closed Friday because of an influx of box jellyfish.

PF Bentley/Civil Beat

Emergency medical services were called twice to Hanauma Bay for three people who had bad reactions to the stings before the park was closed. All three refused treatment.

According to recent research, jellyfish blooms are something we can expect more of in the future. Civil Beat reported that the numbers of  box jellyfish –Hawaii’s most venomous jellyfish – have increased over the last couple decades.

Jellyfish numbers aren’t just growing in Hawaii. According to a recent study by the University of British Columbia, jellyfish populations are growing everywhere, especially in areas heavily impacted by humans, pollution, overfishing and warming waters.

Jellyfish interfere with many human activities by stinging swimmers, clogging intakes of power plants, and interfering with fishing, according to the UBC study.