Its source is near to the village of Capel Coch, before flowing through Bodffordd and into Llyn Cefni in the centre of the island.

[1] It passes through the flatlands of the Malltraeth Marshes, where the river course was altered in 1824, creating a canal-like straight stretch.

[2] Finally it flows under a bridge carrying the North Wales Coast Railway Line at Malltraeth Sands in the south-west of the island and into the Irish Sea.

Newborough Forest on the southern shore is used by large numbers of ravens as a winter roost, and a peninsula and a rocky islet in the estuary are a breeding ground for shags and cormorants.

There was a ship named after the river built in Glasgow in 1890 by a company based in Menai Bridge.