Sea Snakes: Characteristics, types, habitats and more

The Sea snakes or sea serpents are part of a subfamily known as poisonous snakes, which in turn belong to the Elapidae family. Don´t miss this fabulous article about this species.

Sea snakes were considered at first as a unified and separate family: the Hydrophiidae. But then these creatures were divided into two subfamilies: the Hydrophiinae, or true sea snakes (16 genera with 57 species), and the more primitive Laticaudinae, or sea kraits (one genus, Laticauda, with eight species). Now, let´s learn better about all of them.

Sea Snakes Main Characteristics

In the case of the true sea snakes adults´ length varies from 1 to 1.5 meters although some specimens can reach up to 2.7 meters but it´s not very common.  They live mainly in the coastal areas of the Indian and western Pacific Oceans in waters less than 30 meters since they need to submerge in the seabed to obtain their food. Some species prefer hard bottoms (corals), while others prefer soft bottoms like the mud to hunt their prey.

sea snakes : Yellow sea snake (Hydrophis spiralis)

They have a flattened body with a short tail like an oar, valvular nostrils on the upper part of the snout and elongated lungs that extend along the whole body.

Their scales are very small and, in general, they are not superimposed. The scales of the belly are reduced in size in the primitive species, while in the more advanced forms they are absent. As a result, advanced species can’t crawl and therefore, are defenseless on land.

As for the six species of marine or bungarian kraits (Bungarus), they are not as evolved for aquatic life as the true sea snakes, because although its tail is flattened, its body is cylindrical and its nostrils are lateral. The scales of their belly are enlarged (like those of terrestrial serpents) and can crawl and climb to the ground. Their  typical color pattern consists of alternating black bands with gray, blue or white rings.

Sea snakes can remain submerged for several hours, possibly up to eight or more. This remarkable feat is due in part to the fact that they can breathe through their skin.

More than 90 percent of carbon dioxide waste and 33 percent of its oxygen requirements can be transported through skin respiration.

Finally it is good to know, that sea snakes shed their skins much more frequently than terrestrial snakes. Approximately every two weeks.

This behavior prevents the growth of barnacles and other animals on their skin, which although they don´t damage them directly, the friction resulting from that coexistence does affect the sea snakes´ swimming. However, due to the frequency of the molts, the sea snakes are able to get rid of these organisms.

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Most species of marine snakes usually inhabit the waters that make up the coastal areas of the Indian Ocean, even reaching the Pacific Ocean. It should be noted  that they are not found in the Atlantic Ocean, with warm waters being the ideal habitat for them although some species live in rivers.

Moreover they had important changes to adapt to the aquatic environment such as their tails that currently work as an effective propeller in their swim. In addition to this it is important to mention the change that has occurred in terms of their scales.

¿How do Sea Snakes Reproduce?

Most species of sea snakes are ovoviviparous, that is, the female keeps eggs inside her body until the embryo has fully developed. In this way the egg breaks inside the body of the snake just before the moment of birth. Then the young snakes go directly to the aquatic environment after having fulfilled the proper development inside the mother’s body.

Thanks to this process the offspring are born with a considerable size according to the species. According to the main researches it is known that the sea snakes don´t usually give birth to a large number of offspring: 2 to 9 at the most in each reproduction process

The only exception is the genus ‘Laticauda’ which are oviparous (animals that lay eggs with little or no other embryonic development inside the mother) and lays its eggs on land.

They arrive at the shore to lay their eggs, climbing to limestone caves and rock crevices, where they deposit from 1 to 10 eggs. Adults have an average of 1 meter in length, but some grow to more than 1.5 meters. The longevity record in captivity is seven years

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¿What Do Sea Snakes Feed On ?

The feeding habits of the different species of sea snakes are mainly concentrated in fish-based diets, and even in some cases consume eels. To carry out this process, the sea snakes first bite the preys with their sharp fangs in a very fast way, injecting all their poison while the animal is in their mouth.

This is undoubtedly lethal to the prey since it causes failure in their body´s  tissues and dies immediately. It should be noted that each species has a diet focused on their needs and habitats. We invite you to read our article electric eels to learn about different types of marine species.

Main Species of Sea Snakes

Now let´s learn about the different species of sea snakes that we can find out there. It´s is good to know about all of them to prevent their posonous bites.

The Yellow Sea Snake (Hydrophis spiralis)

This species is the largest of all true snakes as it reaches up to 2.75 meters in length. Its peculiar name is attributed thanks to its body´s color, which usually ranges from yellow tones to green tones and also has some black rings. While it  is young its head has the same color of the body, that is to say in yellow tones, but when it ages it turns black. Moreover, this snake has small tusks in tubular form which contain a lethal poison.

They usually inhabit the rocks and corals of the waters that comprise the part of the Persian Gulf area, that is, encompassing approximately the Indian Ocean to reach Indonesia, including the Philippines, Malaysia and Thailand. The yellow sea snake is in lesser danger according to the IUCN Red List.

Like most sea snakes, the tail of this species is flattened, (similar to an oar), which helps it propel itself through water. Other adaptations to living in the water include nasal passages located in the upper part of the mouth, so that breathing can take place without exposing the body to aerial predators. The nostrils also have valves that close when this species is submerged. They capture their prey by administering their fast-acting poison which kills them and breaks their tissues to facilitate digestion.


This subgroup is also known as Marine Kraits and consists of six species of which four of them are totally marine snake species. They are distributed mostly in the coasts that belong to Asia, specifically in the southeast, even in some islands that belong to the waters of the Pacific Ocean. According to their characteristics they have fulfilled most of the necessary variations to be able to adapt more easily to the aquatic environment.

However, there are considerable exceptions in this group  since they are the only group of sea snakes that go to the shore to reproduce and lay their eggs, that is, these species are considered oviparous. Laticaudids snakes have a very toxic poison; however, they are very quiet and are unlikely to bite people unless they are provoked.

Beaked Sea snakes (Enhydrina schistosa)

This species which is also known by its scientific name  Enhydrina schistosa belongs to the subgroup of the Marine Kraits. It is considered one of the most poisonous and dangerous species in the world, since its poison outweighs the poison of other species. It should be noted that its name is due to the peculiarity of the shape in the frontal area of ​​its jaw, which simulates the appearance of a hook or beak like a snout.

The Enhydrina schista  is perfectly adapted to the marine habitat, and its flattened tail facilitates its  swim and displacement in the water as well as the valves in its nostrils work to breathe without problem. Its body is robust and strong in texture, without leaving aside the sea snakes´ main characteristics of having a flattened body.

Regarding its color, it ranges from dark green to gray in the upper area and white in the lower area, where the shades can vary. They also have stripes reflected in their body of dark tones which extend to the tail. In turn, these bands are thicker when they reach the ends, where they usually merge with each other.

It is known that the Beaked Sea snakes can measure about 140 centimeters in otal length.This popular and dangerous species bases its diet mainly on catfish, fish, balloons, or species of smaller fish, and squid. It is known that this snake places its eggs in the ground, from which 18 offspring are born, even up to 30 usually from September to October.

Wart snakes or file snakes (Acrochordids)

This is another subgroup that makes up the general classification of sea snake species, and they are also known as File Serpents. Only three species make up this subgroup, one of which is totally marine and the other two have adapted a lifestyle in drains and usually in fresh water. It should be noted that these snakes have a huge difference compared to other species, since they are not poisonous.

Snakes Homalopsids (Mud snakes)

This subgroup is made up of about nine species, and is also known by its name of Mangrove Snakes, which are adapted to a freshwater environment and are poisonous. Three of these snakes are considered completely marine and inhabit the tropical waters of the Asian continent and part of the area that makes up northern Australia.

One of the most common species of Homalopsids snakes is the Yellow-banded mangrove snake or yellow-ringed cat snake. This species of distinctive color is unmistakable. They inhabit mainly in mangroves or rivers.

During the day, they remain motionless on the overhanging branches, but during the night they roam the ground to feed on other invertebrates including rodents, small birds and their eggs, frogs, bats and, sometimes, other snakes. They are also excellent swimmers. The mangrove snakes are poisonous and have fangs in the back of their jaws. .

Although they may seem quite docile during the day, it is not recommended to approach them too much, since some specimens may be unpredictable in temperament. As for its length they reach approximately two and a half meters. Another important fact of this species is that it can be domesticated, even if it is a poisonous animal, and this is common in Asia where they are very popular. They are usually found easily in wet swamps and forests.

Natricids Snakes

This is the last subgroup that is part of the general classification of sea snakes species. It is made up by only three species of which none is poisonous.

These snakes are only adapted to live in temperate and subtropical zones, being essential the salt in the marshes for their life´s habits.The Natricids are distributed in the subtropical waters of North America, and are still in the early stages of evolution to fully adapt to the aquatic environments´ characteristics.


The Sea Snakes Poison

Regarding the poison, it should be noted that these species can be lethal because they are usually very poisonous. However, it is important to note that usually marine snakes don´t use their venom unless it is really necessary, for example in the case that they feel threatened or in considerable danger. The most lethal poison known is that that of Enhydrina schistosa.

 A reference on the intensity of the venom of these creatures is that one of their bites is capable of killing at least 50 people.

The poison of the inhabitants of the aquatic environment is 10 times more intense than that of a cobra and it has a neurotoxic capacity capable of destroying the main muscle fibers and in the worst of cases causing kidney defects. It is very important to note that according to various investigations, marine snakes show a more aggressive behavior when they are in heat. On the other hand, this poison contains a neurotoxic capacity.


In addition to biting their prey to ingest them, marine snakes can also bite humans (mainly divers) although it doesn´t   happen so often because of the characteristics of their behavior previously mentioned. It is important to consider that these animals don´t cause confrontations, nor are they known to be aggressive, even marine snakes show no interest for divers in the area where they are. Therefore the behavior of the swimmer or diver is of vital importance to avoid the attack of the marine snakes.

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The deaths that have been recorded by marine snakes´ bite, is mainly due to the fact that the venom of this animal produces a respiratory failure in the victim. But before this happens, the bite produces a series of symptoms, the first being a generalized muscle weakness throughout the body.  After this, the following is a paralysis of some of the limbs, such as an arm or some of the legs, even this paralysis can occur in the face.

In the same order of ideas, after presenting the previous symptoms little by little, the person who has been victim of the sea snake´s poison will be presenting certain difficulties to speak or even eat food.

Then another symptom occurs that is the slow fall of the eyelids, being almost impossible to keep them completely open. It should be noted that each of these symptoms develops one after another, being a sign that the poison is fulfilling its lethal effect.

Then the victim´s vision turns cloudy until it completely disappears .When this symptom arrives,it means that the victim is in its terminal stage, since the following is the effect on breathing which will weaken as the other symptoms increase. Usually at this time the victim enters a critical state, where she can even present seizures and becomes semi-conscious and the next would be death from a respiratory arrest.


When a bite of a sea snake occurs, what must be done in  first place is to recognize what kind of snake it is and follow the steps indicated below.

    • Call to 911 or the local emergency number immediately, especially if the bite area changes color, starts to swell or hurts. Many emergency rooms have antidotes that can help you.
    • Remove jewelry and tight clothing before inflammation occurs.
    • If possible, position yourself so that the bite is below or at the level of the heart.
    • Clean the wound, but don´t rinse it with water. Cover it with a clean, dry bandage.
    • Don´t use a tourniquet or apply ice.
    • Don´t cut the wound or try to remove the poison.
    • Don´t drink caffeine or alcohol, as it may accelerate the rate at which the body absorbs the poison.
    • Don´t try to capture the snake. Try to remember its shape and color so you can describe it, which will help you in your treatment.

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