What Am I?

Just seconds into my second Back Bay National Wildlife Refuge hike last weekend, I came across this large snake lying across the pathway.  I bet you can figure out what it is, at least the major category of it.  Identifying the exact species will be more difficult.  I had to use a field guide back home to figure that out.  But I will attempt to rhyme in clues that will help you figure this out - if you really know your snakes (better than I do) or have a good field guide handy.

I'm never far from H2O
Most likely just a short stone's throw

Where I was in Virginia Beach
My northern limit is in reach

If you see me down in the south
You might think I'm a cottonmouth

But despite what you may suspect
Venom in prey I don't inject

If you grab me and give me fright
I'll give you a painful bite

I swim quite well, go where I please
And can climb very high in trees

You need more clues?  Oh, please don't frown
My background color is quite brown

I've dark blotches on side and back
But bands I do distinctly lack

All the clues are there (with a field guide).  C'mon, you got this one!  Just
Scroll
D
O
W
N
for the
answer!

Curiosity I now slake,
Declaring I'm brown water snake

These snakes usually flee but this one allowed me to take a number of photos and was never aggressive.  On my part, I moved slowly and did not attempt to grab it.  After a few moments, it slowly moved away into some rocks by the bay.  My field guide says they will climb up to 20 feet in a tree, which surprised me.  I assume they are going after baby birds while doing so.  They are often confused with cottonmouths, especially at a distance.  I confused it with the northern water snake, but my field guide by Roger Conant got me straight.  It was a great way to start a hike!  And I saw a cottonmouth (water moccasin) just a few minutes later!