I added a sidescan sonar to my AI a few months ago.
(Post here -
http://www.hobiecat.com/community/viewtopic.php?f=69&t=14541 )
I've been getting the hang of it and collecting some interesting recordings. Here's a couple from my sail on the Parramatta River on the weekend. I've found the AI perfect for mounting the sonar. The slow speed (compared to some stink boats) is pretty much the perfect speed and the stability keeps the transducer pointing in the right direction (horizontal). I do find that power boats and escpecially Rivercat ferrys can almost totally blank the underwater picture for a significant time. You should see the sonar picture after 3 Rivercats converge!
The SS Mortlake Bank located in Homebush Bay. The last 1/3rd of the hull is exposed above water. The sidescan picks up then entire hull including the section not visible above water.

Possible old barge located toward the north end of Homebush bay.

Small boat sunk in approx 7m of water off Putney Point.

Wharfs and pontoons from a marina on Cabarita Point.
