Re: Pontoon transom swim platform
Welcome to iboats.
You might be ahead to buy one, given the stresses those are under I don't know that you could build one, it would have to support several people which at best is 350-400lbs.
We have them at work and they are really beefy, just the aluminum to make one would be @ $300-$400 and then you need to bend and weld it, not something most people can do.
(I am at Bennington and no I can't get you a picture)
Poke around on Google and I am sure you can find something but I don't think this is a do it yourself kind of a project.