There are four species of dolphins that make their homes in rivers. There is, however, one species of river dolphin that makes it's home in saltwater estuaries and the ocean.

River dolphins are not the same dolphins that you would see in the ocean. In fact, river dolphins are only distantly related to sea dolphins.

River dolphins are also the most endangered of all the world's cetaceans.

The five species of river dolphins are the Amazon River dolphin, the Franciscana dolphin, the Indus River dolphin, the Ganges River dolphin, and the Yangtze River dolphin. Each of these species of dolphins are very different from each other.

The Amazon River dolphin is the largest river dolphin in existence. These dolphins are also called Boto, and their scientific name is Inia Geoffrensis.

The Amazon River dolphin is between six and eight feet long, and weighs between 185 and 355 pounds when it is fully grown.

As it's name implies it inhabits the Amazon River, but it can also be found in the Orinoco basins and the upper Madeira River as well. These dolphins have various colored skins, which can be light gray, pink, or brown.

The Amazon River dolphin also appears to be the most social of all the river dolphins.

The Franciscana dolphin, which is also called the La Plata River dolphin, is one of the rarest dolphins in South America. Due to its rarity, there is little known about it.

It grows to be between 4 and 6 feet long, and weighs up to 115 pounds, and its body is a grayish brown color.

Even though sightings of the Franciscana dolphin are scarce, it can be found in the Doce River, in Brazil, and the Peninsula Valdes in Argentina. It can also be found in the coastal waters of Uruguay.

This is the only species of river dolphins that can be found in salt water.

The Indus River dolphin is gray-brown, with a pink belly. It grows to be between five and eight feet, and can weigh up to 200 pounds.

The Indus River dolphin is only known to exist in the Punjab Province and the Sind Province of the Indus River.

Due to its decline in population, the government of Sind, in Pakistan, has given the Indus River dolphin full legal protection, and has also established the Indus River Dolphin Reserve.

The Ganges River dolphin is closely related to the Indus River dolphin. It also grows between 5 and 8 feet, and can weigh up to 200 pounds.

It can only be found in the fresh water rivers of Bangladesh, India, and Nepal.

These dolphins are commonly poached for their oil, which is used in the preparation of bait. Even though the Ganges River dolphin's existence is threatened, little has been done to protect it.

The Yangtze River dolphin, commonly known as the Chinese River dolphin or the Baiji dolphin, is at the brink of extinction.

In 1975, the Chinese government declared the Baiji a national treasure, and began to offer conservation and protection to the species, however, this has done little good, as the dolphin is still endangered by heavy boat traffic, fishing, industrial development, and the construction of the world's largest dam.

The Yangtze River, where the Chinese River dolphin makes it's home is one of the world's busiest rivers in the most populated country on the planet.

The Chinese River dolphin grows to be between four and eight feet, and can weigh up to 360 pounds.

River dolphins are typically smaller than sea dolphins, with longer snouts.

River dolphins also tend to have more pointy teeth than sea dolphins.

Other than the Amazon River dolphin, sea dolphins have proven to be more sociable than river dolphins.

Most species of river dolphins are almost blind, due to navigating muddy waters, but their brains are extremely large and well developed.

Unlike sea dolphins, river dolphins have what resembles fingers on the ends of their flippers, and their dorsal fins are much smaller than that of sea dolphins.