I was a passenger on a Norwegian Cruise Lines vessel returning to Miami after an 11 day Christmas cruise to Aruba and other islands. The date was 3 January 2022. The time was about 4:00 am. The location was about 3 to 5 miles offshore, and the vessel was bound for its docking pier at the NCL cruise facility. Our vessel was heading south. It was dark. My cabin was on the starboard side deck 9. I was sitting on the cabin's patio watching the shoreline and intent on watching the transit on into the river leading to the cruise facility, but we were still several miles offshore and north of the port of Miami. The schedule arrival in Miami was 6:00 am. The sky was clear. Several aircraft were airborne in the area, and the sky was essentially quiet with only a few aircraft in the area. I noticed a fast moving light/object flying on a straight course, coming from west south west ,heading east north east. Since the vessel was heading generally due south, and we were well to seaward of the east coast of Florida I thought it odd that the light/object was on a course taking it east north east, out to sea. It was moving abnormally fast and quietly at a sufficient altitude that I didn't think it odd that it was quiet. As the light/object came closer to our position I was able to recognize that it was dimmer than typical navigation lights and a bit elongated. The center of the light/object was nearly dark compare to the dim edges which suggested an equal sign ( = ) to me. It reached a position almost directly above our cruise vessel then it reversed course without turning around to do so. It just stopped instantly and headed in reverse on the reverse track from which it had been travelling. I could not judge altitude since I didn't know what it was or how big it was. I could not distinguish a shape other than the shape created by the light area ( = ). I made a logical first assumption that it was a search light scanning the night sky on a track west south west to east north east and back. But there was no evidence of a beam linking the light/object to a point on the ground. The air was dry and clear and there were no cloud cover. The light/obect never pulsated, it remained static and quiet, and the shape never changed accept as affected by distance and angle of view. I have 4,000 hours of military flight time as a pilot. I am 74 years old, and have been at sea a lot and in the air a lot on Navy vessels and Navy aircraft.