Back on topic a bit......
I used to be based at both Sumburgh and Bergen and have done the trip in a PA28 4 times, a 172 8 times and a 182 7 times. The weather can be a serious challenge, plan to get stuck at either end for a few days, unless you are very happy in rough IMC, and for the Shetlands/Orkneys take some good tie downs. Other than that good quality survival kit in the aircraft, I once had an unintentional swim after an aircraft went wrong 150nm North east of Aberdeen, it was shatteringly cold, even in the specialist kit we wore as off-shore helicopter crew, and it truly was a fight for survival.
The aircraft has no idea it is over water, so doesn't care, I base that premise on the fact that I spent a year when flying jobs were scarce ferrying singles across the Atlantic from the US to Africa (Admittedly they were C208s with nice smooth turbines) but still singles.
Bergen is my favourite city in the world and the Shetlands have a huge hold on me, both beautiful at any time, but mid-summer, high pressure they become perfect.
SND