Most recently we've been using a Biosonics DT-X on a small boat. Vessel draft and maneuverability is still a concern in shallow waters that frequently have obstructions, especially rocks. So now we're testing a jet ski, on loan from colleagues in Maine. Our plan was to mount the Biosonics on that, but our trial run with the jet ski made us realize just how wet it is. To use the Biosonics, we would have to do some pretty involved retrofitting to have the necessary ruggedness. If the jet ski proves to be a reliable platform, we might put the effort into the retrofit since we like the almost non-existent processing required of the Biosonics data. In the meantime, a colleague here at DMF, Mike Bednarski, showed me his Humminbird 698SI. So we'll take that out and see what sort of eelgrass mapping we can do with it mounted on the jetski.
Here's the whole unit -- transducer, processing unit, and storage (SD card).
Here's an image from the Humminbird website.
We'll be out in a couple of weeks to see if we can image eelgrass and mooring scars in eelgrass. Some folks at the USFWS have put together some great descriptions and details about how they use their Humminbird for habitat mapping here.