The stream that exits the crater area has a pH of about 2.0 and it enters the saline waters of the sea which has a pH of around 7.0 to 8.5. Thus, a chemical reaction takes place at the point of entry into the sea, and here metals and other sulphide minerals precipitate and it is they that discolour the water. Some say that some of these minerals that form include gold and silver.  Possibly a future economic resource!