Whilst Ryanair are getting another 180+ new aircraft, the fact that they are 737-800s is not significant, given that is the same model as all the existing fleet. Ryanair haven't gone for the 737MAX which offers greater fuel efficiency and is the replacement model for the type of aircraft they currently operate.
My understanding from press releases from both Ryanair and Boeing is that the Ryanair order is the first of a new generation of the 737-800 , the new model uses a completely different engine to the current model hence the greater fuel efficiency , Ryanair's total order is for 400 aircraft over 5 years (also the large order is intended to keep the new model out of competitors hands for a while by buying up the production lines for some time) , the greater fuel efficiency is also sighted as the reason they are replacing their entire fleet.
Either way if Ryanair deliver on their promise of a 20% reduction in air fares during 2015 (and keep in mind they are promising us 10 Euro fares to the U.S. by 2018) at the same time as ferry fares are rising between 20-30% then it will be a disaster for ferry operators.
Also not mentioned is the cost impact on imports/exports , if the costs increase then demand for imported goods will fall as export markets shrink as higher end prices to consumers increase (as you can be sure it will not only be transport operators passing the cost increase on) , if those factors cause a drop in freight traffic then several more routes are at risk of closure , including some Irish ones.
I have a bad feeling that if the market is heavily impacted during 2015 then ferry operators will slash and burn many operations and significantly reduce their work forces as a form of punishment to the EU for not listening to them , at that point even if the EU do back down the damage to the industry will be severe.
There may also be an unforeseen external shock to play out yet , it appears that Iraq may unexpectedly descend into civil war , which threatens to drag Iran into the conflict also , if that happens fuel prices will go ballistic , even before sulfur regs come into play , Brent Crude increased by almost 4 dollars in one day on just the fear of an escalating situation in Iraq.