The Pink Amazon River Dolphin is a specific dolphin that the player is able to befriend in Endless Ocean: Blue World.
How to Befriend itAt certain point in the "Be the Best Trainer!" quest, the player will receive notice from Finley of a strange-looking dolphin being spotted in the Cortica River's Upstream area. When the player dives and goes to the Twilight Temple area, they will notice that the dolphin doesn't seem to like their presence very much. One of the team members on the boat will suggest bringing a female dolphin partner along on the next dive to perhaps get the Amazon River Dolphin to be more relaxed and get used to the player's presence. This is because of legends that say that Amazon River dolphins turn into attractive men at night and attempt to woo women before returning to the water at dawn.
The player should then bring along the Red-Tusked Narwhal, who happens to be female. She swims around with the Amazon River Dolphin for a little bit, putting it at ease, and the River Dolphin will then feel more comfortable approaching the player. It can then be befriended.
This particular Dolphin Partner is the only one that is able to move the river debris blocking the Queen's Lake, because it is the only one at full strength in the freshwater environment. The rest of the player's dolphin partners are all species that are more acclimated to saltwater.