The River Crossing Puzzle

Puzzle: Three humans and three vampires must cross a river using a boat that holds two. Vampires can’t outnumber humans on either side. How can they cross?

Answer:

1. Two vampires cross, one returns.
2. Two vampires cross, one returns.
3. Two humans cross, one vampire and one human return.
4. Two humans cross, one vampire returns.
5. Two vampires cross, one returns.
6. Two vampires cross.