It was traveling quite rapidly as if it had someplace urgent to be. As with most water snakes, they are not aggressive unless cornered or made to feel threatened. When that happens, they will bite and it is a bad painful bite, although not poisonous. So if you run into one, don't approach it too close, but you don't need to run the other way either. Respect it's space and enjoy it's beauty.
Plain-bellied Water Snake (Nerodia erythrogaster)