The Cuckmere rises in the north of Heathfield before flowing south then westward towards its principal tributary, the Bull River.  It continues to flow south to join the main stream of the Cuckmere at Hellingly and eventually exits to the sea at Exceat - the only undeveloped river mouth in Sussex.

It is likely that the name Cuckmere, meaning fast flowing, was gained because of the speeds it reaches as it hurtles 100m downwards for the first 4 miles of its journey to the sea.  Its flashy nature is dictated by the impermeable Wealden Clay over which it flows.

The river valley through the South Downs is dominated on its east bank by the Long Man of Wilmington, a 231ft tall figure carved into the chalk and possibly dating from the sixth century.