If you are referring to the Bow look-down mosaic in Ballard's "Exploring the Titanic," that was done by Ken Marschall using B&W Angus stills.
Originally, the mosaic was going to be done in-house by Madison Press, but they were pretty clueless and were making a mess of it, so Ken stepped in.
The mosaic you see was made in the mid 1980s using film images that Ken individually adjusted for scale in a dark room and printed on photographic paper. In a few spots, there was no data and Ken discreetly duplicated some images and inserted them to keep "Bald spots" from showing up.
So far as I know, Ken never did a stern mosaic. Woods Hole was not as cooperative as they could have been and much of the photographic reference Ken got was not really selected ... you get the feeling it was just the stuff on the top of the pile and easy to get to.
Bill Sauder