Especially a rolling boat, which is yawing too.

In a rolling yawing boat, particularly if one is not used to such a flotatory existence, one spends some time, (ranging from one hour to a day, ymmv) gaining their sea legs.

Now there is nothing as annoying and disturbing to this natural occuring cycle, as someone touching/kicking/hitting you, even accidentally, while you are as yet unstable. Actually, the more accidental it is, the more annoying it tends to be - as annoying as someone playing footsie with you while you are trying to watch something very engaging like Star Trek or Ballykissangel.

But even in the afore-mentioned heretic footsie circumstances, one may find excuses to the ignoranmus' actions. On a boat however, where your own stomach, peace of mind and relaxation may be at stake, physical contact, unless instigated, is a taboo, just as talking about Titanic and Ben Gunn is.

So heed my words, would be sea-farer. On a boat, touch not another, and let no other touch you, or cutlasses will fly.