Are their any sailors here who also Brew beer and wine? That's not really the question though. My question is, under the conditions of a sea going vessel, is it possible to brew beer and wine and what extra steps need to be taken to make it successful?
Interesting question. I assume your only real challenge would be movement. If on a large vessel I don't see too much issue, small is a different story.
Just make sure your boil kettles have ample room to not create a splash/spill issue.
Fermentaion may have more challenges, yeast trub may not settle out very well. If there is splashing in the fermenter it may create pressure changes that render a conventional airlock useless.
I would suggest a modified corney keg as fermentor with a 2 bar burp valve, this will naturally carbonate during fermination and be a safe fermentor for the vessel. Use a keg float modification to serve out of the fermentor keg. Won't be the clearest beer, but if you cold crash you should stall any autolysis while enjoying your beer.