Heath & Erik,
No, sorry, I don't have any good idea what the swaths you indicated in the previous post might be. My guess would be they indicate the locations of bathymetry swaths. Surveyed by whom, and for what purpose, I have no idea.
Twenty thousand leagues under the sea (from the Jules Verne novel of the same name) ... A league is the old seafaring term distance. One league equals about three (nautical?) miles. In Jules Verne's novel, 20,000 leagues referred to the total distance Captain Nemo's submarine "Nautilus" had sailed underwater. It did not refer to a depth under the sea surface.