baby jellies most likely.
I understand that baby man-o-war's are washing up as well. They are about as big as a silver dollar with green or blue tentacles all the way around the edges. Don't know if they can sting at that size, but wouldn't risk it.
I think those were discussed in another thread. The are blue buttons or something like that and don't sting. Keep in mind that man o' wars are oblong in shape not round. Oh and they sting from "birth".
Here it is http://www.sowal.com/bb/showthread.php?t=24070