I've been on a lot of cruises. I swear by spending at least one port day on the ship

With fewer people on board, I find it way easier to truly relax on the ship on a port day instead of a typical sea day. Tverdohlib/Getty Images One of the best ways to enjoy a cruise is to stay on the ship while it's docked at least once. Ships are often pretty empty on port days, so spas offer…