Very few aquatic mythological beasts are as scary as the Hydra. It was described by the ancient greek myths as a massive, inmortal serpent with many heads. It also had several
other fearsome supernatural abilities, as well as poisonous blood and the ability to spit acid out of its mouth. Yikes.
It became famous as slaying it was one of the tasks Herakles (perhaps better known as hercules) had to overcome to earn repentance. Of course, their battle was epic. But, as you
may remember from the movie, one key attribute of the Hydra was its ability to regenerate its heads. When our hero cut one, two more would grow back and regain its place.
However, Heracles friend and trusty charioteer, Iolalus came to assist him. Iolalus used a torch to cauterize the beasts wounds, and thus preventing a new one to be grown out of
it. That way, they were able to keep the beast at bay and turn the tide of the battle.