Stokes's Sea Snake

Stokes's sea snake (Hydrophis stokesii) is a large sea snake of the family Elapidae, sometimes placed in its own genus Astrotia. It is found in tropical Indo-Pacific waters from India, Pakistan and Sri Lanka to the South China Sea and the Strait of Taiwan. (The Reptile Database; Wikipedia, general species account)

Its mid-ventral scales form a distinct keel along the belly, often broken into two wart-like tubercles. Colour is highly variable, from cream to brown to black, often with broad black cross bands or rings. It is ovoviviparous, producing small broods of about five young, and groups of thousands have been reported drifting in slicks in the Strait of Malacca. (Wikipedia, general species account)