Have you been seeing these creatures on the beach, along the high tide line?

They are a harmless type of jellyfish, commonly called By-the-Wind-Sailors.
They float on the sea surface and move around by the wind pushing against their sail. These sails are positioned at a 45 degree angle. Some creatures have the sail going on one diagonal, whilst others are on the opposite diagonal. This means that the same wind will push individuals in different directions – preventing all of them from being washed up on the shore to die all at once.
By-the-wind-sailors have stinging cells on their undersides which are used to catch plankton and other tiny sea life just below the surface of the water. The stinging cells are harmless to humans.

Photo: courtesy of “Life of  Sea” website.