Yesterday Egan and I were wading in the water on the beach not far from our house. Egan decided to take a swim and found himself a deeper little pool to submerge in. All of a sudden he was grabbing his crotch with a pained look on his face and not quite screaming. I pulled his suit off and saw there was a blade of sea grass, so I thought maybe he was just weirded out by the feeling of the grass in there. I removed it and pulled his shorts back up. 30 seconds later he was doing the same thing but more urgent this time so I caught a clue, took his shorts off, rinsed the area off and ran to the clinic, which was a block away.
I realized he had probably been stung by Pica Pica ("peek-a, peek-a") those invisible jellyfish-like things that locals talk about, as he was already getting raised mosquito-bite-sized bumps on his (way) inner thigh/bottom/very important parts. Poor buddy! He was uncomfortable but quite impressively stoic and the doctor said that she had a much older boy in this week with the same injury and he was making a huge fuss. Brave Egan! Anyhow, she just swiped it with alcohol and put some hydrocortisone cream on it (and gave us the whole new tube at no cost). The visit was also free of charge, but I'll stop back by and give them a donation.
The best part: We were in the water. Egan got hurt. I picked him up and 5 minutes (literally!) a doctor was examining him. Can't beat that!
Here is some Pica Pica info: http://dermnetnz.org/arthropods/sea-bathers.html and http://ambergriscaye.com/pages/town/picapica.html
Update: as soon as we put the cream on it, he forgot all about the sting. This morning it was barely visible and he seemed unaware of it. After reading up on it, I think the trick was that it was treated so quickly.