The Serpent is long and green, possessed of a dragon's head and the antlers of a deer.
The Serpent's sole attack is to rush at the Master and attempt to knock him off while weaving through the crashing waters of the waterfall. The Serpent has a definite pattern that it repeats. By staying the two central platforms, the Master will be at a prime place to attack it. It's always best to stand on the upper platforms; if the Serpent knocks the Master off, he might be able to land on a lower platform and save himself.
Equipped with the Flame Sword, this fight becomes much easier. Not only is the Serpent often out of melee range, but the double damage will make this fight very short. Magic isn't very effective, but this battle is very easy without it anyway.
When playing Professional Mode, the Master gets the Flame Sword by default.