I'm going on a cruise, and want to know if these would be good for the slippery decks on cruise ships?

Truthfully I would not wear these on a ship deck! Walking, hiking for sure as I'm a big fan. Their not design for that type wet surface and although they'd work, you'd have to be careful. Hope this helps - enjoy your cruise!

Some of the colors pictured are in the Mid size shoe. Are they really different styles, or are they simply showing available colors?

The styles and fit are the same, only difference is color. Hope this helps Paul

Can these be used during times especially for snow days?

I used these to climb Quandary with a fresh dump of 24" of snow in a very wet spring. Yes, I got snow in my shoe as I sunk into extremely deep spots but it handled admirably and dried extremely quick. Very impressed that after such a long/wet/snowy hike that they dried and my feet showed no symptoms of being water logged or uncomfy. You can get those snow covers for boots and they fit these shoes just fine. Mine were the low cuts

I usually wear 11 wide, which size should i order?

I would try the size 11. I usually wear size 12.5, but since that's an oddball size I have to wear size 12's and hope they're long enough. I have narrow feet, but wear large woolSocks most of the time and still have plenty of room in the footbed.Keens will stretch and conform to your foot as you wear them, even if they're a little snug at first.