This rarely-seen jellyfish was spotted 4,000 feet below the sea. | National Geographic Animals

Jellyfish are commonly seen in the ocean; however, they were recently discovered in rare marine lakes. | National Geographic Animals

To celebrate World Jelly Fish Day, we are highlighting the work of Amy Courtney, a comparative neurobiologist and National Geographic Explorer @AmyCourtneyy (X) Amy studies the nervous systems of unusual animals like worms, octopuses and jellies to uncover the basic principles of how they work. “Jelly-like creatures have been floating around in our oceans for around 600 million years. The jellies we see in our waters today are from two different animal groups, the cnidarians and the ctenophores.