Scuba divers have the unique opportunity to encounter incredible marine species that most people only ever see in pictures or on television. From ancient deep-sea creatures to bucket list-worthy encounters with pelagic marine life, , the underwater world is full of unforgettable discoveries. Exploring the ocean also offers a glimpse into Earth’s past, with some marine species having existed long before humans ever appeared.
But which marine species has been around the longest?
From prehistoric sharks to ancient sea turtles, here are 15 of the oldest marine species you can still find beneath the waves today.
1. Frilled Shark
With strange eel-like features, this animal doesn’t look like many of the other sharks we’re familiar with today. It is a shark though; this ancient species belongs to a lineage that dates back around 150 million years and has retained many primitive features. Of all the prehistoric creatures that still exist, the frilled shark might be one of the weirdest marine species ever!
2. Tadpole Shrimp
These tiny crustaceans have been around for more than 200 million years. The survival of these ancient ocean creatures may have to do with the fact that their eggs only hatch when the environmental conditions are favorable.
3. Coelacanth
Once thought to have gone extinct around the same time as the dinosaurs, coelacanths were rediscovered in 1938 off the coast of South Africa. This ancient group of fish dates back more than 360 million years, making them one of the oldest marine species still alive today. These giant, prehistoric-looking animals are still considered endangered and are rarely seen.
4. Sturgeon
Sturgeons are a family of fish that includes 27 species. They date back to around 200 million years and many sturgeon species also have remarkably long lifespans, with some living for more than 100 years. However, overfishing and the illegal caviar trade have made sturgeons some of the most endangered fish in the world.
5. Horseshoe Shrimp
The horseshoe shrimp is a great example of a “living fossil” — an ancient species that has changed very little in appearance over millions of years. This tiny crustacean has existed for more than 200 million years and has retained many primitive features. Unlike many other marine animals, some species lack well-developed eyes and are barely the size of a sesame seed.
6. Greenland Shark
Sharks are one of the most popular marine animals today, but did you know their earliest ancestors date back around 450 million years? Even more impressive is the elusive, deep-sea Greenland shark, which is one of the longest-lived vertebrates on Earth. Scientists believe these slow-moving predators can live for more than 500 years, making them some of the oldest living animals ever discovered.
7. Lamprey
The creepy-looking lamprey looks like something straight from a horror movie. Shaped like an eel, these ancient jawless fish belong to a lineage that dates back around 450 million years. Some species are parasites, using their disc-shaped suction mouths to latch onto other marine animals and feed on their blood and body fluids.
8. Nautilus
The nautilus has survived for more than 500 million years, with its lineage dating back to prehistoric oceans. Unfortunately, despite being one of the oldest marine animals still alive today, it is now at risk of extinction. The nautilus’s unusual and unique shell makes these creatures a prime target for shell collectors.
9. Horseshoe Crab
Like the horseshoe shrimp, the horseshoe crab has remained unchanged throughout its long existence, which dates back around 450 million years. Despite its name, it isn’t actually a true crab and more closely related to spiders and scorpions. Like their distant relatives, they even glow under UV light!
10. Sponges
No one knows exactly how old the sponge lineage is, but fossil evidence suggests that some sponge-like organisms existed at least 890 million years. That’s old enough to make them one of the oldest living species on Earth still around today!
11. Jellyfish
Slightly over 500 million years old, jellyfish are one of the few marine species that have been affected by climate change in a positive way. Some jellyfish populations have actually increased in warmer waters, and scientists believe climate change may benefit certain species in some regions. Who knows, maybe these ancient drifters will still be around in another 500 million years!
12. Baleen whales
This toothless family of whales includes humpback, blue and bowhead whales. A recent discovery of a 36-million-year-old fossil has revealed even more about the history of these ancient animals. They are relative newcomers compared to many others on this list, but their lineage still dates back tens of millions of years.
13. Crinoids
Also known as sea lilies, crinoids first appeared around 480 million years ago. Today, many species inhabit deeper ocean environments, while their fossilised stems can be found in rocks across the globe. Their feather-like arms still play a vital role in the ocean ecosystem, using filter-feeding to capture plankton and other tiny particles from the water.
14. Hagfish
Dating back to 300 million years ago, hagfish are among the oldest living jawless fish. These are eel-like creatures live in the deep ocean, feeding on decaying marine animals and organic matter on the seabed. One of the most fascinating behaviours of hagfish is their ability to produce large amounts of slime when threatened, helping them escape from predators.
15. Sea Anemones
Surpassing the hagfish, sea anemones date back more than 500 million years. Today, many people know them fondly as “Nemo’s home” thanks to their famous relationship with clownfish. Sea anemones form symbiotic relationships with other marine species, providing shelter and protection while also using their venomous tentacles to capture prey.
Help Protect These Marine Species
These fascinating marine animals have been part of our planet’s story for millions of years, but sadly many are now at risk of extinction. Threats such as overfishing, illegal trade, and habitat loss mean we could lose these ancient ocean survivors forever. Make it your mission to explore, appreciate and help protect the incredible marine life that calls our oceans home.
Not scuba certified yet? PADI is a passionate community of underwater enthusiasts dedicated to protecting what is worth saving — including some of the oldest marine life on the planet. Learning to dive will give you the skills and knowledge to become an ocean advocate while experiencing the underwater world like never before.