It then enters County Waterford where it flows through Lismore, before abruptly turning south at Cappoquin and finally draining into the Celtic Sea at Youghal Harbour in Cork.

[3] Its long-term average flow rate of is 89.1 cubic metres per second (m3/s)[3] The Blackwater is notable for being one of the best salmon fishing rivers in the country.

[5] Tributaries of the Blackwater include: Towns along the river are Youghal,[6] Cappoquin, Lismore, Fermoy, Mallow and Rathmore.

Birds Directive, the SPA extends from Youghal New Bridge to the Ferry Point peninsula, near the outflow of the river to the sea.

The tidal flats attract numbers of waders and wildfowl and the species named as targets for conservation within the SPA include an internationally important population of black-tailed godwit as well as nationally important populations of Eurasian wigeon, European golden plover, Northern lapwing, dunlin, bar-tailed godwit, Eurasian curlew and common redshank.