Holy shit! Found here.
The Lion’s Mane Jellyfish is the largest jellyfish in the world. They have been swimming in arctic waters since before the dinosaurs (over 650 million years ago) and are among some of the oldest surviving species in the world. The largest can now be found in the waters around Australia and New Zealand. They are said to be about 6 meters long and have poisonous tentacles that extend up to 50 meters long, which they use to catch passing by fish. They then very slowly drag their pray all the way up to their mouth and devour it.