35 Truly Mesmerizing Jellyfish Photos And Facts

Published May 26, 2016
Updated December 10, 2019

From the one that's immortal to the one that's longer than a blue whale, these jellyfish facts will show you the strangest of the bunch.

Even among the one million ocean species we know of and the nine million we don’t, jellyfish truly are the ancient aliens of the sea. They’ve been swimming Earth’s oceans for over 500 million years — and that’s just the beginning. Discover more wonderfully weird jellyfish facts below:

Cauliflower Jellyfish Facts
For starters, jellyfish aren't actually fish, since they are invertebrates. For this reason, many people think they should be called "sea jellies" instead.Derek Keats/Flickr

Australian Spotted Jellyfish Facts
Because of its incredibly think skin, a jellyfish can get its oxygen from diffusion, and therefore doesn’t need a respiratory system.Irene Grassi/Wikimedia Commons

Beached Man O War Jelly
Jellyfish are literally boneless, brainless, and heartless, and most are transparent.Sonnymt/Wikimedia Commons

Blue Comb Jellyfish Facts
Though they might not have brains, jellyfish do have a nervous system, or, nerve net, with receptors that can detect light, vibrations, and chemicals in the water. Nick Hobgood/Wikimedia Commons

AUSTRIA ANIMALS JELLYFISH FEATURE
Some jellyfish have ocelli, which are eye-like organs that are light-sensitive and can detect up and down motions. Ocelli appear as dark pigmented spots on the jellyfish. JOE KLAMAR/AFP/Getty Images

Deadly Box Jellyfish
The box jellyfish has more advanced vision: its 24 eyes give it a 360-degree view of its environment. It is also the world's most dangerous jellyfish, and the most venomous marine creature. Certain species of box jellyfish can kill a person in just a couple of minutes. Peter Southwood/Wikimedia Commons

Deep Sea Jellyfish
Most jellyfish are found in warm, shallow coastal waters, but there are a few species that live in the cold depths of 30,000 feet. Marsh Youngbluth/Wikimedia Commons

Flower Hat Jellyfish
Jellyfish can reproduce both sexually and asexually. KENPEI/Wikimedia Commons

Freshwater Jellyfish
More than any other creature, jellyfish rule the water. The scyphozoan class of jellyfish are found in every ocean in the world, and the hydrozoan class can flourish in freshwater lakes and ponds. OpenCage/Wikimedia Commons

Glowing Sea Jellies
Green fluorescent proteins (GFPs) from the Aequorea victoria jellyfish species have transformed bio-medical research. The glow-in-the-dark proteins can illuminate specific proteins within the human body to track microscopic activity (for instance, cancer growth).Pixabay

Jellyfish Pink Head
Jellyfish spawn at around the same time every day, usually dusk or dawn. Nataliia Tydir/Getty Images

KUWAIT ANIMAL AQUARIUM JELLYFISH
Most jellyfish live a relatively short life that ranges from a few days to less than a year. Some of the more minuscule only live for a few hours. YASSER AL-ZAYYAT/AFP/Getty Images

Golden Jellyfish
Jellyfish are between 95 and 98 percent water.iSpawn/Getty Images

Jellyfish Lake Kakaban
Despite their poisonous defenses, jellyfish have many predators. Sharks, tuna, swordfish, sea turtles, and even salmon have been known to prey upon the jellyfish. Riza Nugraha/Wikimedia Commons

Lion Mane Jellyfish Facts
Considered the largest jellyfish species, the lion’s mane jellyfish (Cyanea capillata) can have tentacles that extend longer than a blue whale, the largest mammal on Earth.Kip Evans/Wikimedia Commons

Nomura Jellyfish Tentacles
Though some argue that the Nomura’s jellyfish (Nemopilema nomurai), which is found in the waters near Japan, Korea, and China, is the largest jellyfish. At their biggest, Nomura’s jellyfish can reach 79 inches in bell diameter and up to 440 lbs. in weight. Janne Hellsten/Flickr

A Diver Attaches A Sensor To A Large Ech
Jellyfish have been in the water for more than 500 million years. They beat the dinosaurs by a long shot, making them the world’s oldest multi-organ animal. YOMIURI SHIMBUN/AFP/Getty Images

Mediterranean Jellyfish Blue
There are nearly 4,000 different types of jellyfish in the world with hydrozoa jellyfish accounting for at least 3,700 of them. Intandem/Wikimedia Commons

Pink Blue Jellyfish
Environmental stress is believed to be the cause of jellyfish overpopulation. Climate change, pollution, dams, and overharvesting of fish have made it difficult for most other sea creatures to survive, but the adaptive nature of the jellyfish allows it flourish. FRED TANNEAU/AFP/Getty Images

Ocean Comb Jelly
After it was accidentally introduced into Eastern Europe's Black Sea, the comb jellyfish spread rapidly, took over, and wiped out the sea’s $350 million fishing industry, consuming ten times its body weight in food in a single day.Vidar A/Wikimedia Commons

Pair Of Sea Jellies
Watch out—a jellyfish tentacle can sting even if it’s separated from the body. Luc Viator/Wikimedia Commons

Portuguese Man O War
On average, jellyfish kill more people than sharks do. Volkan Yuksel/Wikimedia Commons

Red Jellyfish Glowing
The closer a jellyfish is to the water’s surface, the more likely it is to be colorless. Conversely, jellyfish that swim deeper tend be more colorful. Daniel Chodusov/Flickr

Sea Jelly Bell
Sometimes, crabs will catch a ride on a jellyfish. The tough shells protect the crabs from the jellyfish’s stinging tentacles. Dan90266/Wikimedia Commons

Smack Spotted Jellyfish
A group of jellyfish is called a bloom, a swarm, or a smack. A large bloom can contain 100,000 jellyfish.Pixabay

Small Sea Jellies
A jellyfish is one of a few sea creatures that can adapt to ocean dead zones where there is lots of pollution but very little oxygen. Eric Kilby/Flickr

Spotted Jellyfish Tentacles
Because jellyfish feed on fish eggs and larvae, it’s extremely difficult for fish stocks to restablish themselves in marine ecosystems that are dominated by jellyfish. Eric Kilby/Flickr

AUSTRIA ANIMALS JELLYFISH FEATURE
Fishermen harvest jellyfish for their collagen, which has many medical uses including the treatment of rheumatoid arthritis. JOE KLAMAR/AFP/Getty Images

Striped Jellyfish Upside Down
The umbrella-like bodies of jellyfish allow them to pulse their way around the water. This unique movement is called passive energy recapture, and makes jellyfish the most energy efficient swimmers, allowing them to travel 30 percent farther per swimming cycle than they otherwise would be able to.Pixabay

Tentacle Spaghetti Jellyfish
A military drone jellyfish named "Cyro" was engineered to conduct underwater military surveillance. The drone's design mimics the energy efficiency of a jellyfish, and can operate autonomously in the ocean. Wikimedia Commons

Striped Purple White Jellyfish
Jellyfish are passive hunters. Using their tentacles as a net, jellyfish capture prey such as plankton, fish, and crustaceans without much effort.Sanjay Acharya/Wikimedia Commons

Striped Spotted Small Jelly
Contrary to popular belief, urinating on a jellyfish sting is ineffective. Pixabay

Swimming Sea Jellies
For most jellyfish stings, salt water is the recommended fast-acting treatment, as it does not encourage the release of venom. Fresh water usually has the opposite effect, causing the continuous release of venom. Pixabay

Yellow Jellyfish Facts
The immortal jellyfish (Turritopsis dohrnii) ages like Benjamin Button: when a crisis like starvation presents itself, the jellyfish’s cells transform and revert to their earliest form, a polyp, making this type of jellyfish potentially immortal. (Immortal jellyfish not pictured) Harald Hoyer/Wikimedia Commons

Cannonball Jellyfish
Certain non-poisonous species of jellyfish are considered a delicacy in various parts of the world. The Cannonball Jellyfish is the most common cuisine jelly. Mr.TinDC/Flickr


Next, check out the newly discovered glowing jellyfish and see what it looks like to dive with millions of jellyfish. Then, discover seven of the most frighteningly bizarre ocean creatures. Finally, meet some of Earth's most lethal animals.

Briana Jones
Briana Jones is a freelance writer, screenwriter, and artist roaming the hot sands of the southwest. She enjoys the strange and unusual, and green tea.
John Kuroski
John Kuroski is the editorial director of All That's Interesting. He graduated from New York University with a degree in history, earning a place in the Phi Alpha Theta honor society for history students. An editor at All That's Interesting since 2015, his areas of interest include modern history and true crime.