"I can absolutely guarantee that there isn't a single location in Ireland that has been "extensively overfished by boat-based anglers".
Have to disagree, up to a point, but we all share Tim's frustration...
There are marks, remote with long treks from the nearest 'green' road, impossible to get at from the sea due to the terrain and severe currents or simply the length of journey and cost of fuel from the nearest harbour, that still offer
near virgin territory.
A case in point is the coast along north Mayo from Belderrig to Porturlin. It's a bugger to get to and even harder to fish there. There is
no angling pressure from charter or private boats owing to all the issues mentioned above, and there are similar stretches in Donegal and possibly some spots in west Cork, south west Clare, Connemara, south west Mayo and possibly even wee bits of Kerry.
These marks are rare - agreed Tim - but for the intrepid few willing to either trek there over bog (ok, through bog and gazillions of midges) or steam for more than an hour from the nearest pier or slipway...
Midges for our SA friend are like mosquitoes only far smaller.
Don't let that deter you from packing melt-your-skin strength DEET
Not that it will work on the feckers...
I have not been to north Mayo this year but can verify that marks with no boat fishing pressure exist and that their potential remains largely unexplored. We had one memorable trip to a crazy dangerous mark some years ago, the lads tried to get to it from Killala and it just took too long against the prevailing current. The grounds around these rare locations are open to commercial fishing and thus the number of species likely to benefit from these safe havens may be quite limited. But that is not to say that drone fishing or sliding baits or kite fishing can not work there. I have tried balloon fishing with an offshore wind on a few marks and quickly realized that I needed a bigger reel

on account of the cliffs and "angle of dangle" not to mention the seriously quick currents. I am not sure how well you will do around Dublin - there could be spurs and smuts available off Wicklow, but don't be put off from trying it out.
If there is only one certainty about sea fishing, it's that you really have no idea what's coming to your bait next...
Tight lines,
Kieran