Spherical object rotating over itself over the sea.I was driving along the road when at my right, over the sea, i saw a spherical object floating over the sea at 500 meters over the water.The distance from me to the object was approximately 5 or 6 kilometers far from the seashore, in the middle of the sea.At first sight i thought that it could be a helicopter. But looking carefully i saw that the object was only a sphere of colors white and grey.The object was rotating over itself.It wasn't a balloon in the water, it wasn't a meteorological balloon and, of course not a helicopter.When i stopped to take a photograph it dissapeared. I was searching up and down, left and right, but nothing was there. What is it?