Per Wikipedia :
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Hydrophiidae
Sea Snakes : Except for a single genus, all sea snakes are ovoviviparous; the young are born alive in the water where they live out their entire life cycle. In some species, the young are quite large: up to half as long as the mother. The one exception is the genus Laticauda [which are the kraits], which is oviparous; its five species all lay their eggs on land.
TAXONOMY : Sea snakes were at first regarded as a unified and separate family, the
Hydrophiidae, that later came to comprise two subfamilies: the
Hydrophiinae, or true/aquatic sea snakes (now 16 genera with 57 species), and the more primitive
Laticaudinae, or sea kraits (1 genus, Laticauda, with 5 species). Eventually, as it became clear just how closely related the sea snakes are to the elapids, the taxonomic situation became less well-defined. Some taxonomists responded by moving the sea snakes to the
Elapidae, thereby creating the subfamilies
Elapinae,
Hydrophiinae and
Laticaudinae, although the latter may be omitted if
Laticauda is included in the
Hydrophiinae. Unfortunately, no one has yet been able to convincingly work out the phylogenetic relationships between the various elapid subgroups, meaning that the situation is still unclear. Therefore, others opted to either continue to work with the older traditional arrangements, if only for practical reasons, or to lump all of the genera together in the Elapidae, with no taxonomic subdivisions, to reflect the work that remains to be done.
http://en.wikipedia.org/wiki/Sea_snake