Transducer Shooting Through Hull Install

[Smesh]

So I'm trying to install my raymarine dragonfly transducer into a Malibu X13 and have come up woith a plan, but before I finish up the install, I thought I would run it by a few of you. First of, I know shit about kayaks. I've only used them a few times. Second, my kayak has no way to mount the transducer on the outside of the hull, without it hanging down in such a way that it is likely going to get ripped off on the beach the first time I use it. There is no ready to install hole, there is no deep track or recess. Nothing in the shape of the hull allows it to be tucked away safe even if I'm willing to drill. So....

I researched as much as I could find and then bought a Rubbermaid container that would fit, and cut the bottom off. My plan is to use plumber's putty to create a seal to the inside of the kayak and fill it with water. Thing is, I've read mixed results about this. Several posts I've read on the net suggests this is gonna suck monkey balls and the returns on the display are going to be very poor. Any input before I go the next step?