Moon jellyfish swim in a fish tank at the Sunshine International Aquarium in Tokyo June 13, 2007. REUTERS/Issei Kato (JAPAN)

Despite the word fish in their names, jellyfish are not actually fish. They are invertebrates.


REUTERS/Max Rossi

Jellyfish are seen in a new aquarium display dedicated to 45 different delicate species at the Paris Aquarium, France, January 16, 2019. REUTERS/Charles Platiau

Mediterranean jellyfish (Aurelia Aurita) are illuminated by green lighting inside a tank in the Palma Aquarium on the Spanish island of Mallorca August 31, 2011. REUTERS/Enrique Calvo (SPAIN - Tags: ANIMALS TPX IMAGES OF THE DAY)

A jellyfish floats in the Mediterranean sea off the south coast of the Balearic island of Mallorca August 7, 2006. Sweltering temperatures sweeping Europe have brought a plague of jellyfish to Spain's eastern seashores, forcing holidaymakers to stay out of the sea. REUTERS/Dani Cardona (SPAIN)

A jellyfish swims in a giant spherical tank at the World of Jellyfish aquarium in Prague, Czech Republic, February 3, 2020. REUTERS/David W Cerny

Jellyfishes swim in an aquarium of the Monaco oceanographic museum March 3, 2011. Prince Albert II of Monaco and his fiancee Charlene Wittstock will celebrate the gala diner at the oceanographic museum of Monaco following their wedding on July 2, 2011. REUTERS/Eric Gaillard (MONACO - Tags: ANIMALS ENVIRONMENT ROYALS)

Jellyfish are seen in a new aquarium display dedicated to 45 different delicate species at the Paris Aquarium, France, January 16, 2019. REUTERS/Charles Platiau

A medusa floats in the sea near the Adriatic town of Split, Croatia February 18 2005. Large number of jellyfish have been noticed in the Adriatic in last few months forcing local scientists to examine an eventual link with global warming. NO RIGHTS CLEARANCES OR PERMISSIONS ARE REQUIRED FOR THIS IMAGE. REUTERS/Matko Biljak MB/AA

A group of jellyfish can be called a bloom, swarm or smack.
REUTERS/Charles Platiau

A jellyfish swims off the island of Salamina, Greece, August 23, 2018. Picture taken August 23, 2018. REUTERS/Stelios Misinas

Jellyfish are seen in a tank during a media tour before the opening of the Inbursa Aquarium in the wealthy neighbourhood of Polanco, in Mexico City May 30, 2014. The Inbursa Aquarium has 48 exhibits with thousands of specimens distributed in five big tanks and many other ponds, local media reported. The aquarium will open its door on June 11. REUTERS/Tomas Bravo (MEXICO - Tags: SOCIETY ANIMALS TRAVEL)

Mediterranean Jellies swim past a viewing tank during the preview for "The Jellies Experience" exhibition at the Monterey Bay Aquarium in Monterey, California, March 30, 2012. The new $3.5 million exhibition features 16 jellyfish species from around the world in a collection of live and interactive displays, according to Monterey Bay Aquarium officials. REUTERS/Richard Green (UNITED STATES - Tags: ANIMALS ENVIRONMENT SCIENCE TECHNOLOGY)

A jellyfish floats in the Mediterranean sea off the south coast of the Balearic island of Mallorca August 7, 2006. Sweltering temperatures sweeping Europe have brought a plague of jellyfish to Spain's eastern seashores, forcing holidaymakers to stay out of the sea. REUTERS/Dani Cardona (SPAIN)

Jellyfish swim in a fish tank at Palma aquarium in Palma de Mallorca on the Spanish island of Mallorca July 16, 2007. REUTERS/Dani Cardona (SPAIN)

Jellyfish can eat small fish and zooplankton.


REUTERS/Antonio Bronic

Some of the largest jellyfish have been reported weighing almost 500 pounds.

REUTERS/Fabian Bimmer