The sea monster is identified!

Rincewind was followed for several minutes by a very large creature when we were about 80 miles SE of Nantucket. It was swimming in the wake of the boat, about a foot below the surface of the water - only the fin and the tail were visible. The outline of the creature was sort of visible to the eye, but did not come out on camera images. However, I found a You Tube video that looks exactly the same as our beast - so, it was a "basking shark" - the second largest fish in the world (behind the whale shark). It eats plankton, so there was no danger of Rincewind and crew being eaten. They frequently grow to more that 20 ft. long and this looked like a fully-grown specimen! Here is the URL of the You Tube video - http://www.youtube.com/watch?v=c-fEUaS21ds