This webpage has a thorough description of a setup of a Garmin transducer on a kayak. It looks like the project rapidly advanced to a Humminbird side imaging sonar. (Thanks to Mike Sacarny, MIT for pointing out the sonar projects on this site; I previously used the same website for information about remote controlled helicopters for mapping. Just scroll down to the list of projects at the bottom of the home page.)
I liked the idea of using a portable car emergency power pack. As we learn about operating on smaller vessels, we'll have to move away from the generator. Also, the generator is heavy and stinky, so for shorter surveys, a battery alternative is ideal.
What mapping software was used for the bathymetry? I assume something like ArcGIS. What about the side imaging? Was it SonarTRX or a higher-end software like Caris or Hypack or was it mosaicing of screen grabs? Can something like Hugin (which Mr. Illsley provides links to elsewhere in his website) be used to stitch photos together, and then something like ArcGIS or MapKnitter or QGIS be used for the orthorectification?