Couple of observations:
1) My table manners are awful, and I blame shipboard life. I scarf, and then I relax. Eating like a civilized human now requires concentration; shame on me.
2) While I was in the very nice and absolutely semi-formal dinners at my union HQ/training school, I noticed a perfect litmus test that allowed me to pick out all of the working mariners vs. the continuity captains and bench warmers at dinner: look at how a sailor sits as he eats dinner. The dust-gatherers and can't do-ers sit at ease. Junior officers and active sailors who have recently served on ships or served relatively recently on ships with a somewhat lively motion sit in an entirely different manner: one foot under the seat, as is proper, and the other cocked out to one side, on the outside of the chair legs, braced against the deck, and placing tension on the legs, just waiting for the inevitable roll. It's all very unconsciously done, and when I pointed it out, I got some nods and acknowledgments, as well as a few adjusted seats.