This monster from Greek mythology is called a hydra and is significant because it is the antagonist in many Greek myths including the Second Labor of Hercules. The hydra is a serpent like monster that grows multiple heads in the absence of the first.
A Siren isn't really a sea monster but sailors have told tales of these beautiful women that sing to you and seduce you into their trap of bloodlust. They are said to eat the sailors alive or drowned them deep in the ocean.
This spectacular color panorama of the center the Orion nebula is one of the largest pictures ever assembled from individual images taken with NASA's Hubble Space Telescope. - Credit: C. O'Dell (Rice University), and NASA