[3] The Croatian Ministry of Agriculture considers this larger body of water as the total area of the bay for the purposes of regulating mariculture, with a length of 28 km (17 mi; 15 nmi), a maximum breadth of 6.1 km (3.8 mi; 3.3 nmi), and the depth largely between 20 and 29 metres (66 and 95 ft) meters.

The climate of the area is Mediterranean, characterized by mild winters and dry summers, with three times more rain in the rainier than in the drier months, during which the mean precipitation do not exceed 40 mm (1.57 in).

The bay is under the intermittent influence of fresh water from the river Neretva, naturally more pronounced in its outer and central parts and during the season of high discharge and/or strong Western winds.

According to the concentration in nutrient salts and the quantity of phytoplankton, the bay may be characterized as a naturally mildly eutrophic system.

The favorable hydrological conditions for seashell cultivation have been recognized since Ancient times: remnants of oyster farming dating back to the Roman Empire have been found in the area; the first written documents on oyster gathering there are from the 16th century, and those which relate to seashell culture from the 17th, as recorded in the Republic of Ragusa.