Sharks should not be the ones to be feared in the oceans. Jellyfish are actually the biggest killers of the ocean. They are responsible for around 100 human deaths per year, about twenty times more than how many sharks are responsible for annually. The Box Jellyfish is responsible for causing the most human deaths. They’re know as “the world’s most venomous creature,” and that name is no joke. Their venom pierces through a human’s skin, travels into the bloodstream, and causes cardiac failure within minutes.