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Of course it varies from cruiseline to cruiseline, but there are some standard inclusions that should be noted:
*Cabin (room & board)--you can choose from a number of different options here when booking that range from small two-person cabins inside the ship to large suites with balconies. Your location on the ship also affects the price, as some decks are more "desirable" than others due to the height off the water and accessibility to amenities.
*Meals (almost all)--Typically your breakfast, lunch and dinner as well as snacks are included. Water is also usually included. There are a number of choices for all of these including snack bars, restaurants, diners, and those legendary 24-hour buffets (yes, you really can gain 10 lbs in a week).
*Entertainment--Including shows, music, trivia games, scavenger hunts, karaoke, ice sk
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*Transportation between ports of call--Obviously...this is why the boat moves.
*Use of pool and/or gym and all amenities (sauna, pool towels, pool chairs, hot tubs, etc)--Usually there are numerous pools and gyms. You can take spinning, yoga, Pilate's, or aerobics classes. There are walking trails, hot tubs, saunas, and all of the pool luxuries you can fathom.
*Crew-organized games and activities (parties, lectures, classes)--Typically there are launching parties at the onset of the cruise. There are also crafting classes, educational classes, pool
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*Movies--Both in room and in a cinema setting.
*TV Access--Sounds basic I know, but I was amazed at how "normal" TV was when we were sailing around the Caribbean!
*Services (turn down, housekeeping, etc)--It is amazing how pampered you will feel aboard these liners. You have a room steward whose job is to make you (and some other temporary residents) happy for the length of their stay. While the gratuity you will leave for their services at the end of the week is not included, they will readily turn down your covers, clean the room, fold your tossed-on-the-floor clothes, make towel animals (on several cruise lines although I think Carnival made it most popular--and seriously, some of these are incredibly good!), and generally pamper you and try to earn a serious tip.
*Children's programs/activities--Most large liners have a huge itinerary especially for kids of all ages (starting around 3 on average). These are games, activities, crafts, dances, and all-out fun. True baby-sitting will cost you extra, but it doesn't cost you anything to send them on an "activity" while mom and dad have some alone time.
Photo credit: Savannah Grandfather, Michael Cowan