How to Identify the Brown-Lined Sea Snake (Identification Guide)
A slender marine venomous snake identified by fine longitudinal brown stripes or lines running along a pale body, distinguishing it from banded sea snake relatives.
Read the full Brown-Lined Sea Snake encyclopedia entry →Key identifying features
The Brown-Lined Sea Snake is best recognized by its longitudinal striping pattern, a departure from the crossbands or rings seen in many related sea snakes. Instead of encircling bands, this species shows narrow brown to dark olive stripes or lines running lengthwise along a lighter background, giving it a streaked rather than banded appearance. The body is slender and evenly proportioned, without the extreme head-to-tail taper seen in some burrowing sea snake species.
Coloration & pattern
The background color ranges from pale gray to yellowish or tan, with several narrow brown stripes running along the length of the body from behind the head toward the tail. These lines may be continuous or slightly broken, and their number and intensity can vary between individuals. Some specimens show a faint dorsal stripe along the spine in addition to lateral lines. The belly is typically pale and unmarked or only lightly speckled, contrasting with the striped upper body.
Head, eyes & scales
The head is moderate in size, not dramatically small or large relative to the body, and is covered in the large symmetrical head shields characteristic of sea snakes. Eyes are moderate in size with round pupils, positioned toward the top of the head to aid vision while swimming near the surface. Nostrils sit dorsally and close with valves when submerged. Body scales are small and smooth to weakly keeled, arranged in numerous rows around the mid-body typical of the genus.
Size & body shape
Adults generally reach 70 to 100 centimeters in length. The body is moderately slender and roughly uniform in girth along its length, tapering gradually into a laterally compressed, paddle-shaped tail adapted for propulsion through water. This even body profile, lacking the pronounced swelling seen in some relatives, helps distinguish it in the water when the striping pattern is not clearly visible.
Range & habitat where you'll see it
This species is found in coastal waters of the Indo-Pacific region, favoring shallow reef flats, seagrass beds, and sandy or muddy coastal shallows. It is a fully marine species that does not venture onto land and is typically encountered near the surface or in shallow water close to shore, sometimes seen from boats or while wading in calm coastal areas.
How to tell it apart from look-alikes
The defining distinction from most other regional sea snakes is pattern type: stripes running the length of the body rather than crossbands or rings. Species like various banded sea snakes show clear rings encircling the trunk, while this species' brown lines run parallel to the body axis. Careful attention to whether markings run lengthwise or wrap around the body is the most reliable identification cue, since overall coloration and size can overlap with several other slender sea snake species in the same region.
Frequently asked questions
What pattern distinguishes the Brown-Lined Sea Snake?
Narrow brown stripes running lengthwise along the body, rather than the crossbands or rings seen in many other sea snakes.
What color is the background of its body?
Typically pale gray, yellowish, or tan, with a paler, mostly unmarked belly.
How large does this species get?
Adults typically measure 70 to 100 centimeters in total length.
Where does it live?
Shallow coastal waters of the Indo-Pacific, including reef flats, seagrass beds, and sandy or muddy shallows.
How can I tell it apart from banded sea snakes?
Check whether the markings run along the length of the body (stripes) or wrap around it (bands) — this species shows lengthwise lines.