Snails are fascinating creatures. They're hermaphrodites. The diameter of their shells can be microscopic to over a few feet. Their greatest weakness is lack of moisture, and salt can kill them.
But the fascinating facts don't stop there. Snails also have bizarre sleeping habits. They can sleep for hours at a time or up to three years.
According to a 2011 study, researchers found that the sleep cycle of snails tends to follow a two to three-day period, as opposed to the 24-hour cycle of humans. Even more interesting, they found that within that two to three day period, snails will experience seven periods of sleep over the first 13 to 15 hours, followed by 30 hours of alertness and activity.