Facts about Jellyfish

Jellyfish around Koh Tao

Jellyfish in Koh Tao

Cool Facts About Jellyfish

Jellyfish are not fish, they are invertebrates. Many think they should be called ‘sea jellies’. Jellyfish and jelly-like sea creatures come in all different shapes and sizes. Animals that are typically called jellyfish belong to the Phylum Cnidaria, which includes over 10,000 species.


Jellyfish aren’t overly common in Koh Tao, however a variety can be spotted around the monsoon season when the ocean temperature drops slightly, at dive sites like Chumphon PinnacleTwinsWhite Rock and Hin Pee Wee.

Here are some cool facts about our jelly friends….

They can clone themselves

Did you know that Jellyfish can clone themselves? If a jellyfish is cut in two, the pieces of the jellyfish can regenerate and create two new organisms. Also if a jellyfish is injured, it may clone itself and potentially produce hundreds of offspring.

Who Wants to live Forever?

Did you know that certain jellyfish are immortal? The jellyfish has two stages of life, namely the polyp stage (juvenile phase) and the medusa stage (adult phase). The Turritopsis Nutricula has earned the name of the Immortal Jellyfish, as it is able to change between these two stages depending on the environmental conditions and in times of stress. Some jellyfish on the other hand have a very short life span lasting only a few hours or days.

They Are Thick Skinned

Did you know that jellyfish don’t have or don’t need a respiration system? Because of their incredibly thick skin, they get their oxygen from diffusion through the water.

And heartless….

Did you know that Jellyfish are literally boneless, brainless, and heartless, and most are transparent. Although they do not have a brain, they do have a nervous system, like a nerve net that can detect light, vibrations, and chemical changes in the water. They are between 96-98% water.

They are most venomous marine creatures on the planet

Did you know that jellyfish have eye-like organs to detect light changes and changes in motion? These cells are called ocelli, and they appear as dark pigmented spots on the jellyfish. The box jellyfish has the most advanced vision in the jellyfish family.


It has 24 eyes which gives 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..!!

As well as living at some of the deepest depths of our oceans

Did you know some species of jellyfish live at depths that exceed 30,000 feet, which is 9,144 metres.

Did you know that jellyfish can reproduce sexually and asexually. They also spawn at the same time every day, usually dusk or dawn.

They Can Glow in the Dark

Did you know that jellyfish can glow in the dark? Specifically the Aequorea Victoria jellyfish produces green fluorescent proteins that have now been transformed for medical research. These proteins can illuminate specific proteins in the human body to track microscopic activity e.g. cancer growth.

Larger Than A Blue Whale

Did you know the largest species of jellyfish is the Lion’s Mane Jellyfish? The largest reported spotting of this jellyfish was in 1870. The Bell of the jellyfish was 2.3 metres and the length of the tentacles was 36.5 metres, which is longer than a blue whale.


Oldest Animal in the World

Did you know that jellyfish have been on this planet longer than dinosaurs? They have been around for roughly 650 Million years. That makes them the world’s oldest multi-organ animal. The collective nouns for jellyfish are a bloom, a swarm or a smack. A large bloom can contain 100 000 jellyfish.

Did you know jellyfish kill more people annually than sharks do? Also, you can still receive a sting from a tentacle even if it is separated from the jellyfish body. Treatment for a jellyfish sting is not urine, contrary to popular belief. It is actually recommended to use salt water, as fresh water encourages the release of venom.

Space Travellers

Did you know in 1991 jellyfish travelled to space so that scientists could examine how microgravity affected them. The jellyfish multiplied in space. When they came back to Earth, the scientists discovered that the space-born jellyfish couldn’t deal with gravity, so they swam upside down.


Jellyfish are amazing creatures. I have been lucky to see a selection of jellyfish while diving in Koh Tao. The best time to spot jellyfish is around Monsoon season. I have seen Lion’s Mane, Rhizostomeae and the infamous Box jellyfish. Although they can be dangerous, they are beautiful to watch and appreciate from a distance.

Author: Heather Nicholson (PADI DM #370231)

Crystal Dive Koh Tao

7/1 Moo 2
Tambon Ko Tao
Koh Tao
Surat Thani

E-mail: [email protected]

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