Things can get cramped on a mega ship that holds thousands of people. The largest ship at sea, Harmony of the Seas, has awesome new features and great stage shows and amazing specialty restaurants. But it also can sail with 6,780 people onboard ... and there are only four pools for all of them to share. If you choose a mega ship on a busy week when the cabins are full, expect to see lines snaking across the deck for the water slides and around the lunch buffet on sea days.
Problem solved! If you hate that feeling of being part of a large crowd, choose a ship with a smaller passenger capacity, or a line that's known for its spacious and open design, such as Viking Ocean Cruises.