There isn't a whole lot known about the giants of the sea, the sednas. This enigmatic creature was only discovered in the early 20th century and still remains a mystery to many. Sednas are massive creatures, up to 300 feet long and up to 80 feet in diameter, and scientists aren't sure what they are or where they came from. Some speculate that sednas are the remains of an ancient, giant sea monster that went extinct long ago. Regardless of their origin, sednas are an impressive sight, and their uncanny ability to live at the bottom of the sea makes them even more fascinating.