It seems like sailors are always depicted as mopping. The obvious term, 'swab the poop deck comes to mind', and I can think of numerous world war sailors in dancing, mopping routines.
I've had a boat, albeit small at 24ft, and everything was always wet. I didn't bother mopping. I would just hang a towel and dry my feet when I needed. Why did sailors always have to mop or where did this legend originate? Surely they weren't using fresh water, were they?
If I had to speculate, I'd say it was busy work. The more I think about it, I guess it could be boat maintenance or slip prevention. Thanks!
Edit: auto correct in the title, it should say 'always'
In terms of the cultural impact of mopping on ships, I do not feel qualified to comment, however there were several practical reasons for regularly swabbing decks. During the Age of Sail and usage of Ships of the Line, loose powder on gun-decks was a significant fire hazard and danger. Therefore swabbing decks to keep them moist dampened any powder that fell to the floor and reduced the risk of fire. Loose powder would also need to be cleaned up after the guns were used. Regular cleaning of wooden decks slowed down decomposition and was also an import part of discipline, giving a sailor a task to achieve instead of succumbing to boredom or idleness.
Sources:
William Quereau Force, Army and Navy Chronicle, and Scientific Repository, Volume 11 (1840)
Admiral Philip Patton, Strictures on Naval Discipline and the Conduct of a Ship of War, intended to produce a uniformity of opinion among sea officers (1810)
Edit: Syntax
One interesting reason, not mentioned in the other posts, is something they found at Mystic Seaport with the repair of the Charles W Morgan: freshwater makes wooden things rot, salt water keeps wooden things from rotting. If you keep swabbing the decks with seawater, you reduce the chances of falling through them.