At the Lakeview Park Clean-Up, some residents were picking up some branches of a tree when a dangerous Water Moccasin slithered out and dashed into the water. It might be useful to know one when you see it, but the differences between the venomous Florida Water Moccasin (or Cottonmouth) and the wholly harmless Water Snake can be subtle. Here are a few images and links that might help. First, here's a Water Moccasin
Another shot of a Water Moccasin (click for a huge image):
Here's the plain old harmless Florida Water Snake:
Another clue (thanks Ray):
When in water, Water Moccasins move on top of the water - almost as if they were gliding on the surface, like this:
Water Moccasins are to be met with extreme caution. "When a moccasin is nesting or has her young in their nest it will aggressively defend that area," says Ray. "Moccasins have aggressively attacked people."
Water Snakes tend to be partly submerged, partly out of the water, more like this: