Pick out, if you can, the swarm of transparent box jellies in this underwater video captured off the coast of southern Spain.
Filmed on a GoPro camera, the video shows the swarm of box jellyfish - also known as sea wasps and marine stingers, in the shallows off the town of Roquetas de Mar.
According to National Geographic, their venom is considered to be "among the most deadly in the world, containing toxins that attack the heart, nervous system, and skin cells.
It is so overpoweringly painful, human victims have been known to go into shock and drown or die of heart failure before even reaching shore." The US National Ocean Service says that while box jellyfish are found in warm coastal waters, the lethal varieties are found primarily in the Indo-Pacific region and northern Australia.
It is the Australian box jellyfish (Chironex fleckeri) that is considered the most venomous marine animal.