There's a great walk starting at Portstewart Strand (No. 5, to those in the know ;) over the dunes, alongside the golf course and towards the Bann. This would be view starting out:
Portstewart Strand, looking towards Donegal
I know my horizon isn't level on this one - just tilt your monitor or head and it'll be fine. After a decent hike over the dunes you might end up here:
Bann Estuary, towards the west
Most times you can then walk alongside the Bann towards the Barmouth before cutting back inland over the dunes and coming out on the Strand about No 14. Sometimes though the tide is in and this bit you see above is impassable, in which case you have no option but to turn inland and head back over the dunes again. The Bann is at its widest here - a huge expanse of river, populated with Herring & Common gulls and lots of Cormorants. On the other side is the RSPB hide and from there you can get all sorts on the mudflats: curlews, red-shanks and other wading types as well as ducks. This side you mostly get driftwood. It's a very peaceful area - sheltered from the wind and sea and quite beautiful.