We were swimming in the sea on holiday and saw a coin like thing in the sky. Dark Grey. Could not work out what it was as it flew from side to side and seemed to "flip" one side to the other, which made us think it could not be wind current as never seen a kite fly like that. It ascended..descended and went straight but never at speed. Airport was near and it was lower than the flight path descending. Was not a kite. Want to know what it was. We noticed as was circular and flying odd. Lost sight when it seemed to come nearer the bay and off the horizon. I lost sight when it seemed level with the mountain/ hills opposite palma bay. What was this? There is an airport just near...so presumably it would have been on radar?Feelings....skeptical...was something going on we didn't know about...but also same time we know what we saw and never seen anything fly like that. Was not how we wouldhave expected a ufo to fly or look like