Its surface area is about 65 square kilometres (25 sq mi), with a maximum depth of 10 metres (33 ft).

In 1986, the governor of Isahaya began a 235 billion-yen reclamation project of a tidal flat by closing off part of the bay for agricultural purposes with it being completed in 2008.

However, the reclamation project was met with a series of protests from local fishermen, who said that the closing of the bay had caused changes in currents along with mass pollution within the bay, which had affected their catches.

[1] Isahaya Bay is located within the Ariake Sea on the island of Kyushu, Japan.

[2] It covers an area of 65 square kilometres (25 sq mi)[3] and has a mean depth of 10 metres (33 ft).