The Incan Treasure is a one-time salvage item particular to Endless Ocean 2. When the player scans it using the Multisensor, they will see that it is made out of stone, metal, and high density materials.
"Hidden in the capital city of Cuzco by the last Incan king as Spaniards destroyed the empire in the 16th century."
This one-time salvage item is found using the clues from the "Golden Legend" treasure rumor, which tells of the legend of El Dorado, a tribal chief said to be the personification of gold. It can be found in the Sacred Chamber in the Upstream region of the Cortica River, but only once the player has completed the map of this area.
The appraisal reward the player receives for finding this treasure is fifteen thousand pelagos.