That looks awesome!
Can you tell us a bit out the route?
How long was your route? Is camping allowed in the dunes?
It looks like most of those beaches only exist at low tide and the water would come right up to the dunes/ headlands at high tide, is that true?
Slim
The route covered the entire coastline of Donegal from Bundoran to Muff (Yes, that is the name of the town) We rode a bit over 500km and took a lift along the way. You can find out why in a wee blog I've written which covers some of the trip. (See below)
Technically speaking, camping is not usually allowed on the dunes but there isn't actually anybody out there to find you, especially out of season (the summer season runs from Easter until the first week of September).
I'm from this area but not living there any more and had never cycled it until this year.
The beaches exist at all tides but as with any tidal zone, this will depend on Springs and neaps when the water will come higher up the beach. Also in stormy conditions the sea can totally cover the beaches.
http://www.farawayvisions.com/wild-atlantic-way-bundoran-to-killybegs/Let me know if you'd like to know anything more specific. I'm always happy to help.