Wouldn't you just use the bridges like everyone else fleeing the SHTF?
You should really invest in a boat load(pun intended) of those skinny long balloons. You could blow them up and put them in a plastic bag and use that
as a flotation device as you flee across the river and streams.
They are also good for storing water in too as that should be a concern of yours while you are fleeing.
Also when you get to where you and all the other "Flee'rs"(I just made that up)get to where ever you are going and are safe from the
SHTF'ers(made that up too)you can entertain the others by making balloon animals and hats.
I can't believe somebody is spending their waking hours worrying about something so insignificant as crossing a body of water.
What you never learned to swim?