The city closed the beach at Haunama Bay after an influx of jellyfish.
An Ocean Safety Division spokeswoman said about 40 people were stung and lifeguards recommended that the city Parks Department close the popular snorkeling beach.
The visitors center, parking lot, and lookouts on the upper level remain open.
Hanauma Bay is normally closed on Tuesdays, so officials will assess the jellyfish influx on Wednesday and decide whether to open the beach.
I will save my weekly biking to Haunama Bay to swim!