Chunks of Ambergris can be found as salvageable items in Endless Ocean: Blue World. When scanned using the Multisensor, they are shown to be made primarily of stone.
"Ambergris is used in perfumes and some herbal medicines. It's formed in the intestines of sperm whales...Appetizing!"
The appraisal reward for finding a bit of Ambergris is five-hundred and eighty pelagos.