It's a Bushmaster from south america.

Agree with RobertL - looks like a bushmaster from the markings.
Cottonmouths are noted for very 'white' mouth's and contrasting 'dark' bodies (Yahoo Image has a lot).
Vipers (generally) have very wide heads and raised eye's that are normally shielded (horns).
Snakes (as a general rule) can eat things up to three times the size of the largest section of their bodies without stress; of course they can eat a LOT larger prey if they want but it stresses them and makes them less able to escape from threats.
Guessing its body size in the background - Your normal size dog would be a meal...

It looks like a vagina, with fangs...so...wait, I guess it looks like a regular vagina.

Damn cool capture. It's hard to be there with a camera waiting for a snake to yawn.... I know, cause I have tried. None of mine are hots, but still.... very cool capture.

YAAAAAAAWWWWNNN!

Exactly what I thought : Now go to sleep.

thats a bad mother