LEGAL DISCLAIMER - THE SUBMITTER ASSUMES NO LIABILITY OR RESPONSIBILITY IN ANYWAY FOR ANYONE WHO BUILDS OR USES A SIMILAR DEVICE.
Sorry, I didn't take pictures during the build of this device, but will try to display the most appropriate picture for each step.
THE PROBLEM: When the family goes swimming, either in a pool or at the lake, my daughter, who has Cerebral Palsy, would either just have to float around in a life jacket, or be carried around by an adult. Either way she had no independence. Also, because she is so skinny and isn't moving around, she would get cold very quickly, even on a warm day.
Step 1: Collect what you will need.
The chair part is useless for most disabled kids as it provides no support, but can be used without the motor so it isn't a total waste. Please note that I do not work for Canadian Tire or Fluid.
I know there are no Canadian Tire's in the U.S., but I would think that many outdoors or department stores would carry the Fluid line of products. That motor is actually used in a few of their products, so should be easy to get.
You will then need to get some pontoons from the old-style water-loungers or something similar, or rig up something yourself. Check garage sales. Make sure whatever you use or make is wide and long enough to ensure that it is stable and will not flip over.
Finally, use the seating system from one of your old wheelchairs. This one is from our daughter's old Kimba stroller. For obvious safety reasons, we removed all of the belts and restraints. By doing this, the seating is still adjustable, and can grow with the child.
Step 2: Assemble the PVC grid.
Because you can't cut into the shaft in anyway as you would loose steering, use an appropriate sized rubber hose clamp (pictured) affixed to the grid by stainless bolts and then tightened enough to secure the outershaft without being too tight to crush the shaft or hinder steering.
I used long bolts to support the seat from the PVC grid, but stainless rod or more PVC would work too.
Step 3: Finish the seat.
One, it relocated the steering to the centre of the seat, as apposed to the original blow-up chair which was on the right, allowing steering by either hand.
Two, the shaft acts as a pummel, keeping the users legs apart while keeping them inside the seat. Depending on the size of the child, add foam to the shaft to make it bigger. Gaffer tape works nicely to cover the foam and hold it all together. I also added a golf ball to make steering even easier.
The motor is fired by pushing down on the top of the "steering wheel," which is easy to do, and how it comes stock, so no need to change that.
Basically that's it. I really can't do into much more detail as the build and cost will be different for everyone, and the parts you collect to do it. Feel free to contact me at the link above if you want to bounce some ideas or get more detail. Good luck!
BTW - After two seasons of use my daughter has grown out of this, but it still works great. It is free to the first person who has a disabled child the right size that can use it safely. We live near Toronto, Ontario.