object in water 2 feet from boat made a straight right turn at high speed

I was on look out on ocean minesweeper USS Embattle MSO-434 . starboard lookout called me to look at something. it was raining and 7 foot waves. it apeared that the water running off of the deck was making a trail in hte water 2 feet from our starboard bow. when the boat rolled to port the trail was still there even though the water was running of the port side. 
after about 5 mins. it made a straight right turn and left at a high rate of speed. u could hear it moveing through the water like a fishing line. it was about 10 ins long and 3 ins around. it could not have been a porpose or a submarine. we could not see anything under the water because it  was just to dark. i was in the navy 11 years. i am a trained observor
Source of report indicates that date of the event is approximate.  PD