Was up in Orkney this week doing a hotel, and ferried there and back in the van. The route gets in to Scrabster (beside Thurso). Anyway, was meant to be back on 11am boat but it was cancelled due to weather, but they ran the 530 crossing, which was fine until we got to about 1/2 way. Captain came on giving it the "please be seated erm.... it might get a bit bumpy".
We were on deck 6 and the waves were up at our window! The swell was, according to the capt, 30-50ft, this massive ferry was getting chucked about like a raft. Sideways tilting felt like about 30-40 degrees maybe not that much but there were people falling out of seats/plates etc crashing about.
Got back down to the car deck and there were cars leaning against each other, one 4x4 was up on a volvos bumper, and the van had moved 4feet and was resting on another car and inches from this big harley davidson - every car had shifted about.
It was awesome fun watching the waves coming in, until you realised this was a ferry with 200 cars on board.....

I can now see why containers fall off the side of cargo ships etc!