Jellyfish drift gracefully through all the world’s oceans—from the warm, turquoise waters of the Caribbean to the icy depths of the Arctic. Their mesmerizing, undulating movements and delicate tentacles make them some of the most captivating marine creatures to observe. Despite their beauty, jellyfish are surprisingly simple animals. They have no brains, blood, or hearts and are composed of about 95% water and only 5% solid matter. This unique structure allows them to move as if they are one with the currents, effortlessly navigating their aquatic environment. Although typically associated with the ocean, some species of jellyfish can also be found in freshwater environments. These freshwater jellyfish are much smaller than their saltwater relatives and are completely harmless to humans. They add to the surprising diversity of life in lakes, ponds, and slow-moving rivers. It’s important to remember that while many jellyfish pose no threat, all jellyfish species have venomous tentacles—some so mild humans barely notice them, others capable of delivering painful or even dangerous stings. Species like the box jellyfish can be life-threatening, making it vital to understand the jellyfish native to any area where you’re diving or swimming. Wearing appropriate exposure protection is always recommended to reduce the risk of stings.

Diving with jellyfish is an exciting experience but always use caution and keep a reasonable distance. Like most marine animals, the colder the water, the larger the species get, and jellyfish are no exception. Avid divers plan dive trips to the more frigid waters of the Arctic to swim with the world’s most giant jellyfish, the Lion’s mane. If you like to live on the adventurous side, you can join the many divers who travel to Australia to dive with one of the most beautiful jellyfish in the world, but also the most toxic, the box jelly, also known as the sea wasp. No matter where you dive in the world, you are sure to see at least one jellyfish along the way. Click here to learn more about specific types of jellyfish and where you can see them.