Durnesh Lough is located about 12 kilometres (7 mi) north of Ballyshannon on the R231 road, just past the village of Rossnowlagh.

At one time there was a natural outflow, but that has been replaced by an artificial channel flowing to the sea, which admits some seawater.

[4][3] The lagoon forms the main part of the Durnesh Lough Special Area of Conservation, other parts being the dunes, the beach, a cobble storm-beach, drumlins covered with sand and a small seawater lagoon.

In the parts of the lough with a muddy substrate, the emergent vegetation includes yellow iris, mare's tail and reed canary-grass.

[3] Fish species in Durnesh Lough include sand goby, flounder, rudd, three-spined stickleback, sea trout and the critically endangered European eel.