We're soon going on a cruise to the Scottish islands, to celebrate our pearl wedding anniversary, and I'm expecting to see some fantastic scenery from on-board.

Whilst I will take many photos hand held, I was wondering what people's thoughts are about whether to turn steady shot on or off when using a tripod on board (I will experiment, as I have IBIS on a custom switch, and on OSS switch on a couple of my lenses).

My current thinking is to keep steady shot on, as there must be slight movement from the ship, even if it feels stable.

Slight movements are one thing, vibrations from the engine are another one. 
If I want to show the ship „racing“ through the water (i.e. long exposure with parts of the ship in frame) I use the tripod on board (a research vessel that is much smaller than a cruise ship). The difficulty is to find a spot where the deck does vibrate only a little (again, this will be easier on a cruise ship).
As I did those shots with my DSLR I used the mirror lock-up, which did turn shake reduction off.
I think your plan to experiment is a good one as the conditions certainly vary from ship to ship and with sea state. Enjoy the trip!

Oh, just saw that this trip is a distant memory meanwhile…

 

Thanks Prieni

I kept IBIS on and was very pleased with the results - even taking long exposures with ND filters on the front