These appear to be balloons/air pockets of oil and have come ashore in the wind and wild water. I popped one with a stick, felt like a little kid playing with the ick found at the shore, you can tell the jelly fish and these are nothing like that. I have also found shells that have oil residue on them, little spots you can wipe off, but it smells and leaves itself on your hands or towel. But as you can see it is here and there, rather isolated and not all over. It is not like you have to step on them or have no where else to walk, but it is distressing to see.
(as always you can left click on the pics for enlargement)
Have an oil free day
Take Care and God Bless