During the night, on an overnight ferry crossing from Newcastle to Amsterdam 4 years ago, I woke up on my bunk bed and stared out into the blackness of the North sea. I saw a bright light which I assumed at first was a lighthouse - I'd guess about 3-5 miles away. However, the light remained solid and constantly maintained its distance from the ship, as if tracking it.
As I kept watching this phenomena, another light suddenly appeared from nowhere - several miles to the south of the first light. It remained stationary for about a minute before it flew across the sky straight up to the first light. It took a split second to reach it. I know of no aircraft on earth which could cover such a distance at that speed. It was instantaneous.
The two lights stayed together for several minutes, still maintaining a set distance from the ship, before ceasing and then fading into the distance.
In my book, I've seen 2 UFO's - unidentified flying objects. Haven't a clue what I saw.