Living in murky river waters, they have eyes that are tiny and lensless; the dolphins rely instead on echolocation for navigation.

Heinrich Julius Lebeck named the Ganges river dolphin Delphinus gangeticus in 1801, while Johann Georg Wagler coined the genus name Platanista in 1830,[3] a Latin word derived from the Greek "platanistēs", which may be related to the Greek words platē ("oar") or platē ("flat, broad").

In 1853, Richard Owen described a specimen from the Indus and considered it to be the same species as the Ganges river dolphin, but a smaller form.

[3] Based on differences in skull and vertebrae structure, blood proteins, and lipids, scientists declared them to be separate species in the 1970s.

[5][6] The results of these studies were criticized for their small sample sizes and the absence of statistical analyses; by the late 1990s, the two populations were again considered to be two subspecies of a single species.

[6] However, a 2021 study reanalyzed the two populations and found significant genetic divergence and major differences in skull structure; this led to the conclusion that the two were indeed distinct species.

[8] They are not closely related to other river dolphins of the families Lipotidae, Pontoporiidae, and Iniidae, which all independently adapted to freshwater habitats.

Fossil Platanistoidea showed a diversity of cochlea shapes, though Platanista was unusual in that it developed flatter spirals with larger gaps between them.

[13] South Asian river dolphins possess some features that are "primitive" for a cetacean, such as a cecum connected to the gut and air sacs near the blowhole.

[3] In one study sampling 46 Ganges river dolphins, the maximum length and weight recorded were 267 cm (8.76 ft) and 108 kg (238 lb).

The maxilla (fixed upper jawbone) has pneumatic extensions or "crests" on each side which curve around the melon and protrude forward over the rostrum.

[3] The teeth of South Asian river dolphins are curved and longer in the front, where they remain exposed when the jaws are closed.

[3] Living in murky waters, South Asian river dolphins are nearly blind, their tiny eyes having flattened corneas and no lens.

The animal relies on a sphincter-like muscle around the eye to control access to the retina and prevent light scattering, similar to a pinhole.

[18] Outflows of freshwater into the Bay of Bengal have allowed them to swim along the coast, and there is at least one record of an individual entering the Budhabalanga River, around 300 km (190 mi) southwest of the Ganges Delta.

They are most commonly found in stream pools, meanders, and confluences, and around river islands and shoals, which produce relatively stable waters.

[14] Living in shallow river environments with acoustic obstacles, these dolphins echolocate using repetitive clicks spaced 10 to 100 milliseconds apart.

When hunting at the surface, dolphins listen for the movements of schooling fish which are then herded with spins, side-swimming, and lobtailing.

At the mid-surface level, the dolphins use more echolocation clicks to find prey hidden in clutter and vegetation as far as 20 m (66 ft) away.

[18][30] The habitat of these river dolphins intersects with some of the most densely populated areas, leading to intense competition for water and resources.

[19] River dolphins accumulate high amounts of persistent organic pollutants, pesticides, and heavy metals in their system due to being at the top of their riverine food web.

[19] Being nearly blind and relying on echolocation for navigation, river dolphins are also negatively affected by noise pollution from boats.