These beautiful jellyfish float around our waters year round. They average around 8 to 10 inches (20 to 25 cm) and in the Summer will form large schools. While boating a couple of summers ago we saw what looked to be large rocks just below the surface of the water. It turned out to be thousands of these jellyfish covering areas of about 150 feet long and 50 feet wide. The water was almost solid with them. We could see other clusters throughout the inlet we were boating in. It is something I had never seen in my lifetime of living near the ocean. Not sure if that bodes ill or good.
These guys are considerably larger – about basketball size. Normally they have long, hair-like tentacles flowing beneath them. For some reason this one didn’t. They also sting and this one managed to get me a couple of times while I was swimming with it. The sting was equivalent to stinging nettle and caused some redness. It is advisable not to touch them, even when found dead on the beach as they can still be potent.