The pontoons are off of Thingyverse, considerably enlarged and split into 2, because not even a CR-10S4 is big enough

I've added the loops for the ropes and replaced the original Thingyverse treadway bridge parts with my own.
I've given the first 2 a coat of Plastidip rubber spray paint - while it seems to look the part, it didn't seal the interior quite as well as I had hoped, but they still seem quite functional: