Jellyfish have no brain or bones or skeletons  and they are in warm or cold water. jellyfish are like a wobbly jelly and they can eat like little plants like phytoplankton and copepods. look like an octopus after they have huge tentacles and  they can be many color jellyfish . jellyfish live in all kinds of ocean water, sometimes tropical or cold water. Jelly kill more people more than sharks.