So the question still stands, why remove east-coast SAR cover instead of using Shannon for top-cover? I'm not criticising, I'm just perplexed. There is a spare 92 at Shannon, too, though presumably would need crew. If there had been a north-coast incident the same night then the closest SAR cover would have been Waterford... ( CHC / ICG also cover NI waters under an extension to the contract ).
Possible reasons include:
Shannon aircraft already on other tasking
Shannon aircraft or crew u/s
Poor weather at Shannon meaning that the Dublin crew had an easier time getting to the scene
Ireland isn't a big country so getting Waterford up the east coast wouldn't cause excessive delay (notwithstanding the ability of British SAR assets to join in, as already mentioned). Let's face it, as soon as Humberside get a job or go u/s, there is nothing on the British east coast between Inverness and Lydd! This is not a dig at Bristow, merely a relevant comparison.