Northern Water Snake

One of the permanent resident species on Bull Creek is the Northern Water Snake.  Visitors frequently are alarmed at the sight of "a copperhead in your swimming hole."  They are frequently confused because of similar coloration but the water snakes neck bands are complete rather than the "Hershey Kisses" pattern of a copperhead.  They tend to darken with age.
They are frequently found patrolling the edges of the stream, cruising in and out of underwater rock crevices in search of crawdads and small fish, or anything else they can get their mouths around.  Wikipedia says they can also project themselves out of the water, up to 2 m in height to attack prey such as small birds and insects.
Like many snakes, they will bite if threatened and release excrement and musk as a further deterrent.  Their saliva contains a mild anticoagulant, which can cause the bite to bleed more but poses little risk to humans.
Our friend pictured here was found by our neighbor Larry Whiteley.  It was just starting to devour a perch head first.  By the time we went back for a camera it was almost done, with just the tail protruding from its mouth.  With its jaw displaced for swallowing, the head had an ominous triangular shape but the pupil was round, not to be confused with a venomous water moccasin.

Copperhead out for a swim

Speaking of Hershey Kisses, for years I have been reassuring neighbors that if it is swimming in the creek, it isn't a copperhead so leave it alone.  Then several years ago, a friend was at the creek crossing and got this picture.  The copperhead was crossing at the shallows but was proving the exception to my rule.  It pays to observe carefully.  Click on the pictures for a larger view.

A good resource for the Snakes of Missouri is on this Missouri Department of Conservation web page.