8 small reddish jellies in area where local say they have never been seen before

We were vacationing on the beach outside my in-laws' home in Cetraro Marina south of Naples, Italy the first week of July, 2014. We'd been swimming happily in the seemingly clean ocean for two weeks, when one day, three of the four children in our party came screaming out of the water with nasty red welts on their feet. On closer inspection, we found that there were small, reddish-coloured jellyfish in the water. We fished a total of eight of them out, before the area seemed clean, though no one wanted to go back in the water that day. My in-laws say that in the 40 years they've lived there, no one has ever seen a jellyfish on the beach there before. The next day they were gone and we swam again happily. Using the PERSEUS species list, I'd say the jellyfish we saw were most likely mauve stingers.