The Amrita bottle is a salvagable item in Endless Ocean 2. This is made of high density.
Some Indian mythologies state that this elixir grants eternal youth. Unfortunately, it takes 1,000 years to make.
How to Find it
This is a one-time treasure, found in the Cavern of the Gods, using the clues in Okeanos Tablet 4. This can only be found after re-opening the cavern.
The appraisal reward is 11,000P.