Do lobsters really scream when you put them in boiling water?

Answer

No. That is a myth.

Lobsters do not have vocal chords and are therefore incapable of screaming. The sound heard is actually steam being released from between the animal's body and its carapace (or shell covering)

This however, does NOT mean that the lobster dies pain-free. In fact, though it cannot see or hear very well, it is has a very sensitive tactile sense (or sense of touch). FYI: Zoologists have confirmed that it takes the average lobster between 35-45 seconds to die. And yes, they do feel pain.

THE ABOVE IS INCORRECT

Although this issue has been the subject of intense debate over the years, modern studies tend toward the hypothesis that most invertebrates, lacking a central nervous system, do not feel pain. For more information, consult: http://www.cbsnews.com/stories/2005/02/14/tech/main673989.shtml