I went out today to the lagoon (Fort Pierce, FL) to get some sand, ghost shrimp, and water for my 5 gallon aquarium, and I caught a strange invertebrate, which at first I thought was a jellyfish.
It looks basically like a clear ball of gelatin, about a half inch long, with white spots all throughout the body. Out of the water, this is all I can see, but in the water I've noticed a smaller part of the body, about a 1/4" long that it looks to be using to swim.
Unfortunately, it's too weak a swimmer to swim against the intake of the filter, so I have it in it's own little section away from the intake.
I've caught a few of these other gelatinous balls around seagrass beds, mainly just the clear with white spots variety, and another that was clear with thin, bright yellow stripes through the body.
I would take a picture, but my camera's battery died, and I can't find the charger.