The Glaslyn is a very fine river but it is also one with some major contrasts in its character. The upper section between Llyn Gwynant and Llyn Dinas is a worthwhile run but keep an eye out for look out for trees and low bridges.The section from Llyn Dinas and past Beddgelert provides a splendid class II run. Below Beddgelert the river is swelled somewhat by the confluence of Afon Colwyn.
The character then changes dramatically at the entrance to the Aberglaslyn Gorge. This legendary section may be short (only about 1.5km) but it is certainly action packed, particularly if it is attempted in full flood when it becomes a very committing grade V run.
Below the gorge the valley opens up and the river transforms into a tranquil meander down to the coast at Porthmadog.
There is a National Trust facilitated access agreement for Afon Glaslyn. There are significant restrictions on the use of the river by paddlers. The gorge itself is closed to canoeists and kayakers between March 20th and October 17th. Elsewhere there are minimum water level indicators - if the water is less than 0.75m then access is not allowed. For more details check out the Glaslyn Arrangement leaflet on the Snowdonia Active website: http://www.snowdonia-active.com/upload/documents/Glaslyn_Arrangement_leaflet.pdf