The seas, oceans, lakes, and rivers inhabit a large number of animals. There are different known species or newly discovered sea animals. These animals have shown unknown characteristics that allow them to be classified as rare sea animals.

We can find these rare sea animals worldwide, in shallow waters or at great depths, feeding on different prey and adopting different ways of life.

If you want to know the characteristics, food, and habitat of the rarest sea animals in the world, you have come to the right place.

Table of Contents

1. The Bob Marley spider

Bob Marley Spider Female allotype - sea animals
Image of Bob Marley Spider Female allotype by R. Raven (source)

For its ability to live whether the sea is low or high, as the song High Tide or Low Tide by Bob Marley says, it got its name Bob Marley Spider.

The Australian researchers who discovered this new species of intertidal spider gave it the scientific name Desis Bob Marley. 

It has learned to build a kind of silk chamber that fills with air to breathe. It was seen in Queensland (Australia) for the first time in 2009.

The new species have characteristics similar to those belonging to the spiders of the genus Desidae, which are marine. So much so that it usually takes refuge in the shells of barnacles, in corals, or seaweed at high tide. 

It has reddish and brown tones, orange legs, and elongated and greyish structures covering its entire body to camouflage during threats. The female spiders are giant than the males, reaching 9 and 6 millimeters in length, respectively.

Its range of distribution is still unknown, although, at the moment, its presence is confined and duly recorded in the intertidal zones of the Great Barrier Reef, along the northeast coast of Queensland.

Scientific NameDesis Bob Marley
HabitatGreat Barrier Reef, Queensland

2. The Casper octopus

Casper octopus - sea animals
Image of ghost-like Casper Octopus by NOAA (source)

This ghostly-looking cephalopod was discovered by chance in 2016 during a US National Oceanic and Atmospheric Administration (NOAA) mission in deep waters off Hawaii. 

In one of the dives in which it was about collecting sediments, the underwater robot’s camera was able to film at about 4,290 meters below sea level the movements of a small octopus hitherto unknown to science.

With such a peculiar physique, it is not surprising that it is known as Casper, referring to the cartoon series and the film Casper, the saint ghost. 

It has only been possible to confirm that it is an incirrate octopod (which does not consist of fins on the sides of the head).

It lacks the chromatophores (pigment) typical of octopuses, so it has a semi-transparent gray color resembling a cartoon character.

They lay their eggs in sponges attached to metal-rich nodules used in the manufacture of mobiles and computers, which could endanger their survival.

Scientific NameN/A

3. Obama Fish

Obama fish - sea animals
Image of Obama fish alive in a holding tank by R. L. Pyle (source)

In appreciation of their decision to expand Hawaii’s Marine Protected Area, scientists from the Bishop Museum and National Geographic named a new species of fish, Obama.

It was discovered in June 2016. The data collected so far shows that this species of the Tosanoid family lives in waters about 90 meters deep within the Papahanaumokuakea marine area.

This area is located in the reserve (or National Monument) expanded by then-President Obama. The scientists will officially recognize the scientific name once they publish the results of their discovery and the morphological details of the fish through a specialized scientific journal.

Scientific NameN/A

4. Hermit crab with coral house

Hermit crab with the coral house - sea animals
An individual Hermit in an aquarium with the coral (left) and removed from its host coral (right) (source)

The most common hermit crabs use seashell or mollusk shells for protection. However, researchers from the University of Kyoto (Japan) discovered a new hermit crab species characterized by occupying and moving small fragments of mobile coral behind its back. 

In 2012, Japanese researchers observed that some of the coral samples of this type kept in museums and laboratories contained what appeared to be small crabs. These samples were obtained from the shallow waters of the Japanese Amami Islands.

After several years of studies and searching for live specimens off the coast of Japan, researchers Momoko Igawa, Makoto Kato have described the hermit crabs in question. 

The curious occupants of mobile corals belong to a species hitherto unknown to the scientific community. 

The new species is named Diogenes heteropsammicola, and the details of its discovery have been published in PLOS One journal.

Scientific NameDiogenes Heteropsammicola
HabitatJapanese Amami Islands

5. Species with the Batman mask

 Species with the Batman mask - sea animals
Image of lateral stout tubercles of bryozoans which resemble a Batman mask (source)

A scientific team led by a UB researcher has discovered 20 new species and two genera of bryozoans, colonial and aquatic invertebrates that can form mineralized skeletons. 

The new species were found during five oceanographic campaigns, between 2008 and 2010, within the framework of the Atlantis project of the Spanish Institute of Oceanography (IEO).

The study identified the most bryozoan species at a depth of 1,000 meters in the depths of the South Atlantic Ocean. 

The most surprising species is similar to the mask of the comic book character Batman. The animal has been named Biconcavus batmani.

Scientific NameBiconcavus batmani
HabitatSouth Atlantic Ocean
Discovered2008 – 2010

6. A glowing shark 

 A glowing shark - sea animals
Image Glowing shark during daylight (top) and its luminescent form at night by Jerome Mallefet (bottom) (source)

It is bioluminescent and shines in the dark. Its small size is also surprising: it does not reach 30 centimeters in length and weighs less than 900 grams. 

It has been recognized for more than 18 years, but it was not until 2017 that it was identified and named: Etmopterus lailae. 

It is a member of the glowing shark family; it was discovered about 314-384 meters deep in the Pacific Ocean, in the Leeward Islands of Hawaii.

It lives in Hawaiian waters (USA), and although it is not known for sure why it shines, it is believed that it does so to ensure that it is mating with the correct species. 

Or it shines as camouflage to blend in with ambient light and protect itself from predators or as a lure to attract small fish or other prey.

This species has been very little studied due to its size and lives in very bottomless waters. They are not easily visible like other sharks.

Its head has a strange shape and has a vast and bulging muzzle, where the nostrils and the olfactory organs meet. 

Scientific NameEtmopterus Lailae
HabitatPacific ocean, Hawaii
DiscoveredKnown 1990, Named 2017

7. A whale with four teeth and a dolphin snout

whale - sea animals
Image of Arnoux’s Beaked Whale by Ciorano (source)

In June 2014, a biology professor found the body of a half-buried whale on the Pribilof Islands of St. George, in the Bering Sea (Alaska).

The surprise was great when they realized that it was a new species, never before described. Before the discovery, the first researchers believed they were in front of Baird’s beaked whale. 

However, a later examination determined that the animal’s meat was too dark and the dorsal was too large for this species. 

At 7.3 meters long, the cetacean was smaller than Baird’s bill. And it was not a baby since its teeth were old and yellowish.

After tracking the Pacific basin and analyzing DNA samples from 178 whales, the scientists concluded that they were dealing with a new whale species. 

The scientific community only knew of two types of Berardius; Baird beaked whale, as mentioned above, and the Arnoux’s beaked whale (Berardius arnuxii), which lives in the Antarctic Ocean. The find indicated that there is a third species of Berardius in the North Pacific.

Scientific NameN/A
HabitatBering Sea

8. A very elusive giant fish

Rare Giant Fish - sea animals
Massive two-ton Mola tecta washed up in California beach (source)

Despite measuring eight feet and weighing more than two tons, this giant fish has remained hidden in plain sight for centuries. 

In 2017, scientists finally managed to find this elusive specimen in Australia, South Africa, Tasmania, New Zealand, and Chile after years of searching. 

They have named it swindler sunfish or Mola tecta (a term derived from the Latin tectus, disguised or hidden). The carcass of this giant fish was found on the coast of Coal Oil Point, near Santa Barbara (California).

After reviewing the specialized bibliography, biologists have agreed to indicate that the Santa Barbara animal belongs to the Mola tecta species of the sunfish genus. 

For the first time, a specimen of this species has been discovered in the northern hemisphere. The first specimen of this species known to scientists was located near Christchurch, New Zealand, in 2014. 

The species Mola tecta were scientifically described in a study published in 2017, becoming the first fish of its genus to be described in the last 130 years.

It is morphologically different from the other members of the genus because the front of its head and the ridges on the top and sides are not bulging.

Scientific NameMola Tecta
HabitatNorth Pacific Ocean

9. Shaped like a mushroom

dendrogram - sea animals
Image of Lateral view of Dendrogramma by Jorgen Olesen (source)

They are shaped like mushrooms, but they are sea animals, they live at the bottom of the sea, but they are not mollusks or jellyfish. They are new to science, but possibly they have inhabited the Earth, unchanged, for 500 million years.

In 1986, zoologist Jean Just, a researcher at the Museum of Natural History in Copenhagen (Denmark), collected the sample from 1000m off the southeast coast of Australia.

He discovered a total of 18 specimens of tiny beings that are difficult to catalog. They are 8mm long, and the top disc is barely over 10mm.

The analysis work was so complicated that it was not until 2014 that the finding was made known. The new genus has been scientifically named Dendrogramma (family Dendrogrammatidae ), and, based on the samples analyzed, it has two different species.

The name Dendrogramma refers to dendrograms, tree-shaped diagrams used in biology to illustrate evolutionary relationships between organisms.

The new Dendrogramma enigmatica and Dendrogramma discoides are multicellular animals. They are asymmetrically shaped and have a gelatinous layer between the inside and outside of the body.

The closest relatives to dendrograms would be jellyfish and ctenophores. The researchers have also found morphological similarities between the new dendrograms and a group of jellyfish-shaped animals that lived 600 million years ago.

Scientific NameDendrogramma Enigmatica

10. Puffer Fish that builds circular nests

pufferfish - sea animals
Image of pufferfish carving mysterious circle (source)

Scientists had been trying for more than 20 years to find the origin of round patterns about two meters in diameter with geometric designs from the seabed of Oshima, a volcanic island in the Pacific Ocean. 

A circular structure about two meters in diameter first appeared in 1995. In 2011, researchers from the scientific journal Nature identified a small pufferfish, about 12 centimeters long, building one of these structures. 

It is a new species of the genus Torquigener that is not the typical poisonous pufferfish famous for accidents in Japanese restaurants.

These specimens have a structure of thorns and colors that do not correspond to those of their relatives. In addition, these fish have only been found so far in this Japanese region.

The male fish build these nests to attract females, and in addition, the ridges and grooves serve to minimize the effect of currents and, possibly, avoid predator attacks.

First, the male fish creates a big circle. This figure begins to dig small furrows linearly using their pectoral, anal, and caudal fins.

It swims at different angles, always following a radial direction so as not to lose its geometry. The nest’s central part is the most delicate because it will be where the female fish deposits its eggs.

With the circle, the grooves, and more elaborate nooks finished, the second step begins: fine-tuning the exteriors and defining the furrows. 

This work aesthetically polishes the masterpiece and helps flatten the central area by dragging as much fine sand as possible. After a few finishing touches and decoration, the male fish is ready to receive the female fish. 

Scientific NameTorquigener Albomaculosus
HabitatOshima, Pacific Ocean, Japan


These are the rarest exotic sea creatures discovered recently, some having weird names. There are still many more creatures yet to be found.

Some animals have completely bewildered the scientific community and opened the gate for a new investigation to be carried out. 

However, Nature hasn’t stopped surprising us. There’s no doubt in the coming years, we will find more new sea creatures.

(Last Updated on April 20, 2022 by Sadrish Dabadi)

Ankur Pradhan holds a bachelor’s degree in education and health and three years of content writing experience. Addicted to online creative writing, she puts some of what she feels inside her stormy heart on paper. She loves nature, so she is trying to motivate people to switch to alternative energy sources through her articles.