The hot weather over the weekend so many people cooling off at beaches up and down the Sydney coast.
However, many swimmers were shocked by an invasion of bluebottles.
There were reports of incidents all over Sydney beaches from Palm Beach to Cronulla, warning signs were up at Bronte and North Bondi beaches. And Avalon beach was forced to close.
And Sydney may not have seen the end of it.
"Looking at the numbers [of bluebottles] that were around on Sunday, even just the tide coming in and out will drag some of those back in and back out," Rob Townsend, the Life Sciences Manager at Manly SEA LIFE Sanctuary, told Fairfax Media.
How to treat a Bluebottle sting
A major sting to the face or neck area should be treated urgently, especially if there is swelling to the site. In these cases dial Triple Zero (000) immediately and ask for Ambulance.
Remove any tentacles that are stuck to the skin with tweezers or a gloved hand.
Wash the site of the sting with lots of seawater.
Immerse the victims site of the sting in tolerably hot water.
If hot water is not available apply ice packs, avoiding direct contact with the skin by wrapping the ice pack in a towel.
Do not apply vinegar.
Do not rub sand on the area.
Your doctor may provide you with further treatment should you feel it is necessary.