from Discovery.com:

Giant jellyfish like this one are taking over parts of the world’s oceans as overfishing and other human activities open windows of opportunity for them to prosper, say researchers.

In this photo, a diver is attaching a sensor to track a monster Echizen jellyfish, which has a body almost 5 feet across, off the coast of northern Japan.

Jellyfish are normally kept in check by fish, which eat small jellyfish and compete for jellyfish food such as zooplankton, researchers said. But, with overfishing, jellyfish numbers are increasing.

These huge creatures can burst through fishing nets, as well as destroy local fisheries with their taste for fish eggs and larvae.

Photo credit: Yomiuri Shibun/AFP/Getty Images