The City & County of Honolulu closed Hanauma Bay at 1 p.m. on Wednesday due to an influx of jellyfish.
The city says 20 people were stung between 10 a.m. and 11 a.m.
Ocean Safety officials recommended the closure, which was approved with the concurrence of the city Department of Parks and Recreation.
Ocean Safety lifeguards will reassess the situation Thursday morning and determine if Hanauma Bay will remain closed for another day, or if the jellyfish hazard has passed and will reopen for business.
Box jellyfish signs were posted at Ala Moana and Waikiki, but fewer than than 20 jellyfish were counted in those areas. The city says the jellyfish influx is expected to subside by Friday.
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