Glowing disk shaped object hovering in same position for hrs. at times dissapear then soon reappearing in same place .

While working as helmsman onboard Corps of Engineers Dredge Haines in Benton Harbor, Mich., sighted staionary lighted object.  Disk shaped with smaller dome on top the entire object glowing a white/yellow tint as if from internal source.  Positioned farther out to the west over Lake Michigan not showing up on radar I used ships binoculars..  
Then, with closer look, I saw definite disk shaped glowing object stationary in same place for nearly 3 hrs.  Several times while ship went in and out of harbor to dump dredge loads it would dissapear then reappear in exactly same position. This continued from approximately 2am until 5am.  It looked to be above the water not in the water. 
As wheelsman onboard this older ship, I could not watch object continuously while steering ship, but each time as headed west I saw again thru binoculars in same place.  When 3rd Officer left watch at 4am, he said if asked he did not see anything.  
At 4am Chief Officer came on bridge watch (this man had been a Lieutenent in US Coast Guard also had BS degree in Geology.  When I showed this him lighted object he was very intrigued and started to watch closely himself.  
At around 5am eastbound returning to dredge area inside harbor, I steered ship not able to see when he saw it shoot off horizontally immediately moving at extreme rate of speed dissapearing.  
Later, while discussed more, he called local Coast Guard station to report this strange sighting.  Also said that when moving away it had some sort of bright red smaller light showing at very top of upper dome.  
I had never forgotten the incident and have always wanted to report this.  I clearly saw it for over 2 hrs.  I have been going to sea since 1969 USCG first and only time to see this type of object.
Witness indicates that date is approximate.  PD