Carnival Cruise Line is the ultimate mainstream line, with big, lively ships that cater to all age groups and offer impressively deep discounts. The sales are so good, those Caribbean beaches feel within reach as soon as you see the advertised fare. Read our full review. 

Think of these family-friendly, all-ages ships as amusement parks at sea, and you won't be too far off base. They have everything from game rooms to large gyms — and even bowling alleys. Best known for having pioneered "Freestyle Cruising" over a decade ago, this family- and budget-friendly line of mega ships was at the forefront of moving the cruise industry away from the dated traditions of the past. Read our full review. 

Although Costa is owned by Carnival, everything from the food to the crew attitude is influenced by the line’s Italian roots. The ships themselves have over-the-top, gilded décor and the staff members organize wacky contests and lead line dances. Read our full review.

MSC Cruises’ ships feel thoroughly European: The Swiss-based cruise line has partnerships with brands like Eataly and Lego, and the big, glittery ships carry primarily European travelers. The company now has two ships home-ported in the U.S., embarking on Caribbean sailings on select dates throughout the year. Read our full review here.