This Box Jelly or "Sea Wasp" is a medically important Cnidarian, class Cubozoa. Relatives of this species are among the most venomous animals in the world. This species (probably Alatina alata) won't kill you... but they hurt. Some species swim toward light. The inset to the upper right is the business end of the tentacle which delivers venom via a specialized cell, the cnidocyte. Trawled from between 200 meters depth and the surface, Gulf of Mexico, August 2016. Image courtesy of the DEEPEND project.