This Site of Special Scientific Interest is one of the largest areas of common reed in Wales. It is an important breeding site for wetland birds such as redshank and merganser. Water rails may be seen here in the winter. The site takes in salt marsh, swamp and pasture. It stretches from the confluence of the rivers Mawddach and Wnion to almost Penmaenpool. The best place from which to see it is the Mawddach Trail. There is a car park near the River Wnion, where the A493 meets the A496, and one at Penmaenpool.