Very good site Svoberts!!
Sunil,
Take a look @ the cottonmouth pix. Does that look like what you have? Usually a common water snake will not hold it's mouth open, however that's precisely how the cottonmouth got it's name!
Both are agressive.
James,
After the snake is dead, you can positivly identify it as poisonous or not by looking @ it's eyes. All pit vipers in the US have vertical iris's. The only poisonous snake native to the US that doesn't is the Coral snake.
