Spitfire display over Coast

[Milguy22]

Hi guys, I need some help. On Friday 22nd August me and my partner were walking along the pier in dover (due to an early ferry crossing the next morning). I heard the sound of a drone in the distance, scanned the sky and there was a spitfire performing a display quite out at sea. The datum looked to be a ship/ cruiseliner that had departed 20 mins previous to this. Obviously I was too far away to ID it but it was definitely a spitfire as of the shape of the wing and the sound.

Just wondered if anyone knew anything of this or why it was happening?