Yeah the Navy sits because of the danger of falling over if they stand (as a result of the swell of course)
The republican principles bit causes quite a lot of offence after a boozy dinner. I asked one sitter if the Emperor of Japan were here, you would stand wouldnt you ? and then, if I were in France and I didnt stand for M. le president de la republic because I was a monarchist - I would get garotted wouldnt I ? and he said yes (but they didnt stand)