Charter boat captain Erik Rue, 42, photographed the animal, which is actually an albino, when he began studying it after the mammal first surfaced in Lake Calcasieu, an inland saltwater estuary, north of the Gulf of Mexico in southwestern USA.
Capt Rue originally saw the dolphin, which also has reddish eyes, swimming with a pod of four other dolphins, with one appearing to be its mother which never left its side.
He said: "I just happened to see a little pod of dolphins, and I noticed one that was a little lighter.
"It was absolutely stunningly pink.
"I had never seen anything like it. It's the same color throughout the whole body and it looks like it just came out of a paint booth.
"The dolphin appears to be healthy and normal other than its coloration, which is quite beautiful and stunningly pink.
"The mammal is entirely pink from tip to tail and has reddish eyes indicating it's albinism. The skin appears smooth, glossy pink and without flaws.
"I have personally spotted the pink dolphin 40 to 50 times in the time since the original sighting as it has apparently taken up residence with its family in the Calcasieu ship channel.
"As time has passed the young mammal has grown and sometimes ventures away from its mother to feed and play but always remains in the vicinity of the pod.
"Surprisingly, it does not appear to be drastically affected by the environment or sunlight as might be expected considering its condition, although it tends to remain below the surface a little more than the others in the pod."
Regina Asmutis-Silvia, senior biologist with the Whale and Dolphin Conservation Society, said: "I have never seen a dolphin coloured in this way in all my career.
"It is a truly beautiful dolphin but people should be careful, as with any dolphins, to respect it - observe from a distance, limit their time watching, don't chase or harass it
"While this animal looks pink, it is an albino which you can notice in the pink eyes.
"Albinism is a genetic trait and it unclear as to the type of albinism this animal inherited."
A close relation of dolphins, the Amazon River Botos, called pink dolphins, live in South America in the Amazon.