Well, I learned something new today:

diamondback water snake

"When foraging for food the diamondback water snake will hang on branches suspended over the water, dipping its head under the surface of the water, until it encounters a fish or other prey. It is frequently found basking on branches over water, and when approached, it will quickly drop into the water and swim away. If cornered, it will often hiss, and flatten the head and body to appear larger. It only typically resorts to biting if physically harassed or handled. Its bite is known to be quite painful due to its sharp teeth meant to keep hold of slippery fish. Unfortunately, this defensive behavior is frequently misinterpreted as aggression and often leads to its being mistaken for the venomous cottonmouth (Agkistrodon piscivorus), with which it does share habitat in some places. The brown/tan coloration and diamond-shaped pattern also causes it to be mistaken for rattlesnakes, especially when encountered on land by individuals unfamiliar with snakes."