One more thing about returning to the ship. Make sure you look at your daily planner to see what time "All Aboard" is. If I'm remembering correctly, I think it's usually about half hour prior to sailing. Example, if you are in port from 9:00 am - 5:00 pm, ALL ABOARD is at 4:30 pm. The captain will let you know if you need to change your watches, which leads to my next point.
Make sure you keep your watch on Ship Time, and not local island time, if there's a difference. If you do need to adjust your watch, it will be reflected in your daily planner, as well as on the bulletin board on TV.
As others stated, the ONLY time the ship will wait for you is if you are on an excursion that you booked through the cruise line, and that excursion is late getting back.
2007 - Majesty of the Seas (Bahamas)
2009 - Enchantment of the Seas (Western Caribbean)
2010 - Freedom of the Seas (Western Caribbean)
2013 - Golden Princess (Alaska, roundtrip from Seattle)