A water moccasin, S, is a variety of snake, virtually identical to the normal snake but not generated at random. Like regular snakes, water moccasins will hide under items, are poisonous to eat, and have a 27% chance of imparting poison resistance, slightly higher than a snake (26%).
Indiviually, water moccasins are similar enough to snakes that they can be dispatched in a similar manner. However, on top of necessitating poison resistance as usual, their decent speed and appearance in swarms will require efficient crowd control tactics, which may be further complicated if previous uses of the fountain caused pools of water to form. This makes it a potent source of deaths for unsuspecting low-level characters; fortunately, players who do not use fountains will never have to deal with them, while those who wait until after the early game will likely be prepared.
Due to their affiliation with fountain quaffing, they are the fourth most frequent cause of death on nethack.alt.org (next to soldier ants, jackals, and wands); it is common in the #nethack channel on Freenode to exclaim "Go team fountain!" on hearing of a water moccasin death.
Water moccasins are a species of venomous snake well known in the southeastern United States.
- See the encyclopedia entry for snake.