Sea Serpents are perhaps the most famous of the crypto-creatures,with sightings dating back to the middle ages. Ancient mariners feared their ships might be devoured or sunk by these creatures. Sea Serpents are said to live in caves along the shore. Sea Serpents usually described as enormous, many humped, snake-like creatures, have been said to be as much as 200 feet long and 20 feet thick. There have been many sightings but no proof positive identification.