We left on June 3rd, so my experience is a bit dated, but... the north shore beaches of St John was the worst, followed by The Dogs. There were tiny jellyfish in swarms, I later was informed these were sea lice. There were also some normal (not large) jellyfish on most every snorkel. They were easier to avoid than the sea lice. The Safe Sea seemed to work for my boys because the only place they got a rash was under their swimsuit and shirt, where I did not apply the Safe Sea.

The real annoying critter was the bird at Leverick who I caught driking my Presidente!