Cogger’s Sea Snake (Hydrophis coggeri) preserved museum specimen in a jar, labelled Leioselasma coggeri.
Elapidae
Cogger's Sea Snake
Hydrophis coggeri
Cogger's Sea Snake is a banded marine snake recorded from northern Australian waters and the wider western Pacific.
Dangerously venomous
Identification and appearance
Checked marine references describe a yellow-and-black banded sea snake with a distinct head and neck and a vertically flattened tail ending in black. Adult shape varies from small-headed and slender-necked to more robust, so colour alone is not a complete identification.
Other names
Slender-necked Sea Snake, Black-headed Sea Snake
Typical length
The FAO marine reference gives a maximum total length of about 115 cm; AROD separately lists a 120 cm species average. The conflict is retained and no typical interval is inferred.
Head appearance
distinct head and neck
Key identification features
- Yellow-and-black bands along the body
- Distinct head and neck
- Vertically flattened tail with black tip
Where it is found
Northern Australian waters, with the checked taxonomic account listing Western Australia; the wider range includes the Philippines, New Caledonia, Vanuatu and Fiji.
Activity
Marine; the FAO account places it on reef flats at depths of about 30–40 m.
Diet
Mostly ophichthid and congrid eels.
Reproduction
Live-bearing.
Medical significance
Treat any suspected bite as an emergency. Call 000 and follow Australian snakebite first aid; do not wait for identification.
What to do if you encounter one
Keep clear in water or on shore and do not approach to inspect bands or the tail.
Similar-looking snakes
Banded sea snakes are difficult to identify safely from a brief sighting. The checked identification guide distinguishes Cogger's Sea Snake from other Kimberley species by band pattern and count, which are specialist comparisons.
Taxonomy notes
Accepted species Hydrophis coggeri, described by Kharin in 1984; AROD also uses the common name slender-necked sea snake.
Sources checked
- FAO — Sea Snakes species account (2026-09-26)
- AROD — Slender-necked sea snake (2026-09-26)
- Atlas of Living Australia — Hydrophis coggeri (2026-09-26)
- DORIS — Hydrophis coggeri (2026-09-26)
- ANZCOR — Australian snake bite first aid (2026-09-26)
Still not sure?
Compare this snake with more clues.
A profile is a guide, not a reason to approach or handle a snake.