Nature is a harsh and cold mistress, with no care at all to the individual actors playing out life within its system. It's eat or be eaten. Hunt or be hunted. Humans have mostly engineered ourselves out of having to worry about being consumed by other animals but it remains a concern for just about every other organism on the planet.
Like this poor eel. Some lucky camera-wielding diver stumbled upon a raging battle fought between an eel and the sea snake that was trying to eat it. Give it a watch.