That's a tough call there. My first instinct was he doesn't look to dangerous (the head is the general rule, long and thin isn't normally poisonous, and fat diamond shape means run away.) But the banding and the fact that he's going into the water make me say you should probably stay away for safety. After some quick google searches, he doesn't seem to look like any of the dangerous snakes in Louisiana though (unless he's some sort of rattle snake, i couldn't really see the end of his tail.)