The commonly used genus name Pelamis is derived from the Ancient Greek word for "tunny fish", which presumably refers to the habitat or what Daudin thought they ate.

[5] A few recent examples exist of scientists' beginning to use the grammatically correct name Pelamis platura, e.g., Bohme 2003 and the Reptile Database with its page headed Pelamis platura (Linnaeus, 1766), which includes an extensive synonymy of the different scientific names which have been used for the yellow-bellied sea snake.

To further complicate the nomenclature, the taxonomic status of sea snakes is still under review, with recent authors suggesting a dismantling of monotypic genera, such as Pelamis, in favour of a single genus, Hydrophis, in order to reduce paraphyly and better reflect phylogenetic relationships.

Adaptations to aquatic life include the reduced ventral scale size, laterally compressed body and paddle-tail for swimming,[11][12] valved nostrils and palatine seal for excluding seawater, and cutaneous gas exchange for prolonging dive times.

The head is narrow, with an elongated snout; head shields are entire, nostrils are superior, and nasal shields are in contact with one another; the prefrontal scale is in contact with second upper labial; one or two preoculars, two or three postoculars, and two or three small anterior temporals are present; seven or eight upper labials are found, with four or five below the eye, but separated from the border by a subocular.

[20] Their distribution appears to be largely determined by favourable water temperatures, oceanic currents and recent formation of land bridges that have blocked farther dispersal.

The yellow-bellied sea snake has an extensive distribution covering the entire tropical Indo-Pacific, as well as extending to Costa Rica, southern California, and northern Peru.

[23] The favoured habitat for hunting and reproduction includes free floating mats of sea kelp occurring in the Indian Ocean.

[29] These colder water occurrences are believed to be linked to El Niño, among other severe weather events, possibly creating unusually strong, new ocean currents that transport the snakes far off-course.

However these occurrences are believed to be the result of human activity, be it ship discharge, intentional release or via the Panama Canal, as it is not considered a part of their native range.

[38] Due to the wide distribution of the species and relative lack of dispersal barriers, it has been assumed that individuals from different localities represent a single breeding population (i.e., high gene flow).

[13] They are sometimes observed in large aggregations of thousands on the surface of the water in oceanic drift lines, which has been proposed as a strategy to catch prey.

[43] They hunt by floating on the surface of the water to attract pelagic fish that are seeking shelter; prey are captured via a backwards swimming motion and rapid lunge of the jaws.