Click the right arrow as the jellyfish to the right pass into the dotted line, the down arrow as the jellyfish in the center get to the dotted line, and the left arrow as the jellyfish to the left approach the center of the dotted line.
The more accurate you are about hitting the buttons when the jellyfish are in the center of the dotted line, the more points you earn to build up your trick meter to the far left of the play screen.
Jellyfish venom is delivered by barbs called nematocysts, which are located on the creature's tentacles and penetrate the skin of people who brush up against them.
Scuba divers often wear them as well - they provide extra warmth, can make getting a wetsuit on and off considerably more quick and easy and can guard against jellyfish stings.
These range from the bites from a neighbor's dog or cat to bites from fellow humans and spiders to the stings from bees, wasps, snakes, and marine animals such as jellyfish and stingrays.