This isn't really an innovation, but I thought it might help someone. I know the wet mount has been around....
I first mounted my transducer attached to the sail mast of my Hobie Revolution. I zip tied it to the mast and then just added water. It worked, but I didn't like the water in the yak...
I decided to contain the water in some foam.
I bought a foam roller for 10 bucks or so at walmart. After I cut the piece I needed, I jammed it in to the hull of the kayak for extra floatation. Or you can cut and sell more pieces to your non-Hobie friends for $10 a piece. You also can frame the pic of the hot chick on your garage wall.
Cut the transducer section smaller than the actual transducer so the fit is snug.
Take time to shape the foam to match the kayak hull.
I gooped the foam and just added water. The transducer fits in snug and will not come out even if I flip the kayak and shake it, "like a Polaroid camera." I add a water saturated sponge on top just in case the ducer wants to move, but I also use the sponge when I'm done to take out any water from inside the foam.
I have taken it out several times and it works just fine. The water doesn't come out either when I load and unload the yak. If I was to do it over again I would cut the foam at 3 inches or so. I know this wetmount topic is overdone, but just wanted to add.