Assassin Snail Anentome/Clea helena

The Assassin Snail is a freshwater snail or whelk native to Southeast Asia. It is called "assassin" since it eats other snails, sometimes ones larger than it is. (It also eats worms.)

Usually brown and yellow striped (rarely just brown), it grows to around an inch (2-3cm) long. The genus, both genera Anentome and Clea, are freshwater snails (the latter all called "assassin" snails) but the rest of the family are entirely marine true whelks.