Cleaning bathrooms with co-worker at the Rincon, Puerto Rico lighthouse at approximately 5:00 am on 05/16/15. Co-worker saw dark object on surface of water and called my attention to it. I thought it was the island of Desecheo. Co-worker pointed out that the island of Desecheo was BEHIND the object. The lighthouse beam was pulsing but all the other lights in the facility were out. Was using car headlight to illuminate the bathrooms. When we shined the car headlights on the object, the object lit up with an unnaturally brilliant white light. The lights that lit up were around the base of the disk and were round bulb-like. Extremely frightened. Got into car and drove to the guard station at the abandoned BONUS nuclear plant because he is an armed guard. Reported sighting to guard, but guard said it was probably a submarine. Left guard and drove back to the town of Rincon around ten minutes later. While passing the Calypso bar which is around a quarter of a mile from the lighthouse, we looked out towards the ocean and the object was still on the water, but its lights were off. Did not stop to observe it anymore. That morning we reported to the municipality that the lights were out. The electrician (who is my neighbor) reported that when he went to check the lights they were working normally. My co-worker took photos on his cell phone, but they did not come out well. My co-worker moved to the US and I have lost contact with him.