Barefoot when really nice, croc whit waters when walking about, Warmers (neo diving boot) or some leather ones bought off face book (Chinese version of musto)
Dubarry Ultimas when wearing sailing gear - all day comfortable. Barefoot or Musto trainers when wearing shorts. I tried Crocs but found them very slippery on a wet deck and even worse when your feet get wet as there is zero grip internally.