USO, aprox. 1972 off mass. coast about 80 miles out,off the shelf,while traveling on surface in a diesel sub heading aprox N. i was one of the lookouts on starboard side (right) in my sweep of my zone spotted a bright white light on surface behind us, in the time it took to notify the officer of the deck i saw that it was closing rapidly, first siting aprox. 10 miles off, closed within a minute and slowed to our speed (12 Knots) And remained positioned off our starboard side for about 15 minutes at roughly 50 ft away. when first sighted our sonar crew was notified and given its direction, nothing was heard. while it was incoming ,while it was stopped , or when it left us. as stated it marked time with us for about 15 min while the capt and officer observed and capt questioned sonar operator. our guys heard NOTHING then just like it came it left, from 12 knots it accelerated to over 60 knots straight north for a mile then 45 right to NE and gone from view within a min. any normal submerged object accelerating that fast whould have left a major disturbance in the water, no disturbance no noise of engins,screws,or caterpillar drive like in red october nothing at all. our boat did carry Mk 45 nuke torps at that time. after it had gone the officer of the deck asked the capt how to enter this in the log book. The capt said enter what, you saw nothing to put in a log. the OOD said understood sir. nothing was said to myself or the other lookout about it. during the event it looked like someone shining a bright spotlight at surface, no real idea of size. also no disturbance of surface of ocean coming or going.