Actually... i have had a few experiences with this. I had been snorkeling many times before until about a year ago i had never had a problem with jelly fish. I went snorkeling in the dominican republic and a friend and i swam through a school of small jellyfish, and after talking about it at the resort, found out that many others had been stung as well. Then while vacationing in Cozumel over Christmas of this year i was stung again byjellyfish of the same size. There were a lot of them. The stings aren't extremely painful, if the fish are small, just like pin pricks, they can just become annoying because there were so many of them. I am not sure if depends on what time of year it is or what. Hope this helps.