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Sea Snakes: A Complete Guide

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Have you ever seen a Sea Snake in the wild?

These rare and beautiful creatures are often tough to find and sometimes mistaken for eels. Their preference for warmer waters also confines them to more tropical regions, making them even harder to find. Keep reading sea snake: a complete guide to learn everything you need to know about sea snakes.

You might also like to see the Worlds Largest Anaconda.

Sea Snake

This blog will touch on the lives of these little sea snakes; use the headings below to guide you through the blog article:

What are Sea Snakes

In the ocean, Sea snakes are no more than 60 species of highly venomous marine snakes of the cobra family (Elapidae).

There are two independently evolved groups: the actual sea snakes (subfamily Hydrophiinae), related to Australian terrestrial elapids, and the sea kraits (subfamily Laticaudinae), which are related to the Asian cobras. Although these snakes’ venom is the most potent, human fatalities are rare because sea snakes are not aggressive, their venom output is small, and their fangs are very short.

Of the 55 species of actual sea snakes, most adults are 1–1.5 meters long, although some may grow to 2.7 meters. 

In adaptation to marine life, sea snakes have a flattened body with a short oarlike tail, valvular nostrils on top of the snout, and elongated lungs extending the entire body. Their scales are tiny and usually not overlapping, abutting against one another like paving stones.

The belly scales are reduced in size in the primitive species, whereas in the more advanced forms, they are absent. As a result, the advanced species cannot crawl and are thus helpless on land. When swimming, a keel is formed along part of the belly, increasing surface area and aiding propulsion, which occurs by lateral undulation.

Sea snakes can remain submerged for several hours, possibly as much as eight or more. This remarkable feat is partly because they can breathe through their skin. Over 90 percent of waste carbon dioxide and 33 percent of their oxygen requirement can be transported via cutaneous respiration. 

Moreover, a 2019 study of the blue-banded sea snake found a highly vascularized area between the snout and the top of the head, which allows oxygen to be transported directly from the water to the snake’s brain. Sea snakes give birth in the ocean to an average of 2–9 young, but as many as 34 may be born. Another detail added to this Sea Snakes: A Complete Guide.

The six species of sea kraits are not as specialized for aquatic life as the actual sea snakes. Although their tail is flattened, their body is cylindrical, and their nostrils are lateral. They have enlarged belly scales like terrestrial snakes and can crawl and climb on land. The typical color pattern consists of alternating bands of black with gray, blue, or white rings. The yellow-lipped sea krait is a common species with this pattern and a yellow snout.

Sea kraits are nocturnal, feeding primarily on eels at depths less than 15 meters (49 feet). They go ashore to lay their eggs, climbing up into limestone caves and rock crevices, where they deposit 1–10 eggs. Adults average 1 meter in length, but some grow to more than 1.5 meters. The longevity record in captivity is seven years.

Sea Snake facts

Sea Snake

Sea snakes are front-fanged and highly venomous.

A fold in the gums of a sea snake hides the fangs, and the fangs quickly emerge when biting something. Sea snake fangs are fragile and may break off and remain in the wounds of their victims. To counter the problem of having weak fangs, sea snakes have potent venom that can easily paralyze, kill, and begin the digestive process of the fish they target.

Sea snakes evolved from two different snakes (the cobra in Asia and Australian terrestrial elapids). Marine sea snakes are viviparous: They give birth to fully-formed young at sea without laying eggs. Sea snakes require fresh water for drinking and will dehydrate at sea without it.

Where do Sea Snakes live?

They are restricted to coastal areas of the Indian and Western Pacific oceans, from the east coast of Africa to the Gulf of Panama, except for the yellow-bellied sea snake found in the open ocean from Africa eastward across the coast of Pacific to the west coast of the Americas. And that’s why this Sea Snakes: A Complete Guide was put together.

All other species live mainly in waters less than 30 meters (about 100 feet) deep, as they must dive to the seafloor to find their food among coral reefs, mangroves, or on the ocean bottom. Some species prefer hard bottoms (corals), while others prefer soft bottoms (mud or sand) to hunt prey.

Most sea snakes feed upon fishes of various sizes and shapes, including eels. Two primitive groups (genera Aipysurus and Emydocephalus) eat only fish eggs, whereas, Hydrophis specialize in burrowing eels.

Sea Snake Bites

Sea Snake

A sea snake bite is the cause of some fatalities in the Western Central Pacific. Typical victims are fishermen handling gape nets, sorting fish on a trawler, or dragging a net while wading in muddy coastal waters or river mouths. Some sea snakes are gentle, inoffensive creatures that bite only when provoked, but others are much more aggressive.

Even though sea snakes rarely inject much of their venom, so frequently no or only trivial severity of poisoning is recognizable, all sea snakes should be handled cautiously, as this Sea Snakes: A Complete Guide details.

If a snake bite has occurred, the following first-aid procedures are recommended:

If the bite is on an arm or leg, a broad crepe bandage (or material of a similar type) should be wrapped immediately around the area of the bite. The bandage must be tight and extended over the entire arm or leg. Then a splint should be used to immobilize the arm or leg, and hospital treatment must be sought as quickly as possible.

If the bite is on the body, firmly press the area of the bite and look for hospital treatment immediately. 

Ecology and Conservation

Sea snakes are exploited for their skin, organs, and meat. Although some species are taken in great numbers, they are not protected by CITES (A Washington convention). Since 1934, the meat and skin of sea snakes have been used commercially in the Philippines, and local protection of sea snakes has become necessary to avoid overexploitation. 

Sea snakes are also exploited in Australia, Japan, Taiwan Province of China, Thailand, and Vietnam. The local government in Queensland, Australia, has introduced a special license to collect sea snakes. However, most sea-snake fisheries in the Indian and Pacific oceans have not been reported in the literature. Local governments do not control them—another reason this Sea Snakes: A Complete Guide was put together.

Except the Philippines, the impact of exploitation on populations of sea snakes is almost unknown and some populations may already be in danger of extinction. Monitoring and controlling the commercial catch is the only way to maintain a sustainable yield, allowing local governments to intervene before a catastrophic collapse of local populations occurs. 

However, managing sea-snake fisheries and protecting endangered species is impossible without a basic knowledge of the group and the ability to identify to the species level.  

Many sea snake species exist in the Indian and Pacific oceans, but none in the Atlantic or Caribbean. Why is this?

Ocean Current and Climate Barriers

Green Sea Turtle endangered

Not all sea snakes spend their entire lives in the ocean. Some species, called sea kraits -the non-true sea snakes-, can live on land or in water and lay their eggs on land. This limits their range because they need to stay near land to reproduce. 

In contrast, all entirely marine sea snakes are viviparous: They give birth to fully-formed young at sea without laying eggs. This essential trait allowed the pelagic yellow-bellied sea snake to extend its range across the entire Indo-Pacific from an area of origin somewhere in the Coral Triangle of Southeast Asia

However, by the time it reached Central America’s Pacific coast, the “Isthmus of Panama” had formed, fully separating the Pacific and Atlantic oceans. When the Panama Canal opened in 1914, it became possible for an occasional sea snake to enter Caribbean waters accidentally.

However, this species tends to drift with currents, so it is doubtful that enough could pass through the canal and find one another to the east to establish a breeding population. No population of sea snakes has been established on the eastern side of the canal since its completion in 1914.

Sea snakes also could enter the Atlantic Ocean by swimming from the Indian Ocean around the tip of Africa at the Cape of Good Hope. Yellow-bellied sea snakes occur in the waters immediately east of the cape, but two major obstacles prevent them from traveling farther west. And that’s why this Sea Snakes: A Complete Guide was put together.

First, just west of the cape, the Benguela Current brings upwelling of icy water to the coast of southwestern Africa. This current is 200 to 300 kilometers wide, and its water is too cold for these snakes– about 55 to 64 degrees Fahrenheit at the surface – for sea snakes that might drift there to survive for long or reproduce. 

Second, as research has shown, sea snakes require fresh water for drinking and will dehydrate at sea without it. They drink from “lenses” of fresh or brackish water that form temporarily on the ocean’s surface after significant downpours of rain. But the climate of coastal southwest Africa is characterized by a large zone of permanent high pressure, which makes the region very dry with almost no rainfall.

Evolving from land to sea

animals in prince edward island

Sea snakes also could become established by making evolutionary transitions from terrestrial or freshwater habitats to marine habitats in the island systems of the Caribbean. We know that elapid snakes – a family of venomous snakes with short, fixed-front fangs, such as cobras – have done this in the Coral Triangle region. 

Indeed, most of today’s sea snakes originated and evolved into different species in this part of the globe between 2 to 16 million years ago. At that time, this region was a vast wetland complex associated with Southeast Asia and the Australasian archipelago. 

Land and sea are interlaced throughout the Coral Triangle and have been so for several million years. This region has high rainfall, low and variable water salinity, and relatively stable tropical warm temperatures. Throughout much of its geological past, sea levels rose and fell many times, opening and closing marine corridors and causing mangrove fringes and mud flats to form and disappear.

These conditions favor evolutionary transitions from land to sea, and stable, shallow marine habitats have persisted for the past 3 million years.

Similar changes occurred in the Caribbean, but the Coral Triangle is much larger and more complex. Multiple ancestral lineages of snakes occur in Southeast Asia. Four to five times more viviparous (live-bearing), estuarine species within the Coral Triangle than occur in the Caribbean. 

In my view and that of my co-authors, the presence of appropriate lineages of snakes and a dynamic of ecological conditions favored the speciation of sea snakes in the Coral Triangle much more so than in the Caribbean or anywhere else the Atlantic Ocean. Indeed, the Coral Triangle, broadly defined, appears to be the only region where vivipary is characteristic of most estuarine snakes. These snakes live in coastal waters, contacting freshwater habitats.

They were most likely to evolve from terrestrial or freshwater to marine habitats and give rise to sea snakes. And that’s why this Sea Snakes: A Complete Guide is comprehensive.


Could future oceanic and weather conditions permit sea snakes to disperse from the Indo-Pacific to the Atlantic Ocean? It is believed to be quite unlikely. Thus, we do not expect sea snakes to appear on the beaches of Florida, like those occasional snakes that have drifted to land on beaches in California. There is simply no source.

There are signs that some populations and species of sea snakes are in decline or have gone extinct owing to changes in rainfall patterns, water temperatures, environmental contamination or human exploitation. Future climatic changes might bring negative and positive impacts on the biogeography of sea snakes. 

From my experience watching sea snakes swim with graceful undulations over coral reefs, losing them (or any other marine organism) would be tragic and could threaten the health of coral reefs where sea snakes are top predators and considered to be harbingers of ecosystem change.

Summary of Sea Snakes

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It can be said that seeing a snake in the wild is exceptionally special and rare.

Tour groups are not necessarily available to see only sea snakes; however, in some cases spotting a sea snake may be a by-product of another tour in the tropical regions in which they reside.

If you enjoyed reading this blog article, visit our other blogs about our reptiles and alligators.

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