I went for a paddle today, and came across a weird looking yacht. It was a catamaran, but each hull seemed very skinny. And the center of each hull was separated (so it looked like there were 2 hulls on each side). This seemed weird, especially because I thought the length of the water line greatly affected efficiency in going through water, so splitting the hull like that would make it more inefficient.
Google has the answers to everything, including this. Found a web site on this type of ship:
GPS track of the trip is below. Covered about 11 miles. I was listening to the VHF radio as I went to track ships, so I could avoid them. Found out (after I had gone around the Island) that one of the main passages under the bridge on the east side of Treasure Island is closed to boats due to the construction - the same area I had just paddled through! Oops. Now I know. Will avoid that if I do this paddle again.