Today, Bahrain's "two seas" are generally taken to be the bay east and west of the island, the seas north and south of the island, or the salt and fresh water present above and below the ground. In addition to wells, there are areas of the sea north of Bahrain where fresh water bubbles up in the middle of the saltwater as noted by visitors since antiquity. An alternative theory with regard to Bahrain's toponymy is offered by the al-Ahsa region, which suggests that the two seas were the Great Green Ocean (the Persian Gulf) and a peaceful lake on the Arabian mainland.