Whenever I hear of someone crossing the Atlantic, be it in a boat or a barrel, my immediate concern is the huge waves, how would they deal with them?
For sailors, they tend to be going more or less downwind which makes the period longer for a given wave height. Assuming they aren't going straight down wind, their sail also forms a sort of feedback system which keeps them heeled over at a fairly constant angle so there isn't a lot of boat rocking going on.
You can see typical values at http://www.stormsurf.com/page2/papers/seatable.html Note that is in "feet@seconds" and the blue values are typical, the white cells wander off into computational fantasy.