When the player has the Old Sea Map and goes to the S.S. Tidal port in Lilycove City and the player interacts with the woman standing in front of the boat, the Faraway Island event will activate. She proceeds to fetch the captain, who initially claims it's impossible to take the player to the area denoted on the chart, but Mr. Briney scolds him for turning the player away and volunteers to take the player to Faraway Island, even though it is a long way from Hoenn.
After the boat ride, the player enters Faraway Island, a small island with a thick patch of forest. Deep within this forest, the player notices Mew, who flees playfully. After a short game of hide and seek, the player is able to pin Mew in a corner and engage it in battle.
A faded sea chart that shows the way to a certain island.
The Old Sea Map was only released officially in Japan and was distributed in 2005 during the Pokémon Festa event. Like the GS Ball, this event item never reached international players without the use of cheating.
In the manga
Old Sea Map in Pokémon Adventures
In the Pokémon Adventures manga
The Old Sea Map was discovered in the Trainer Tower by Ultima in Bested by Banette. She had been looking for it in order to help her old friend, Mr. Briney, find a way to the Faraway Island. When Ultima called Briney about her find, however, she was shocked to learn that the old sailor had managed to find the island without the map.