The inter tidal area of mud and reed beds close to Pwllheli harbour, known as Pwll Du or the Backwater. Pwll Du is an area behind the Embankment or Cob at Pwllheli harbour, North Wales. At low tide the Afon Rhyd-hir flows through the ‘Backwater’ area, under Embankment Road then flows out into the inner Pwllheli Harbour and onto Cardigan Bay. The land at the Cob, Pwllheli has been protected as a Local Nature Reserve.