Question: what are the big cruise lines?
Answer: Symphony Of the Seas. The 25th ship in Royal Caribbean's fleet, Symphony of the Seas is currently the world's largest cruise ship. ... 
Harmony of the Seas. ... 
Allure of the Seas. ... 
Oasis of the Seas. ... 
AIDA Nova. ... 
MSC Meraviglia. ... 
Quantum of the Seas. ... 
Anthem of the Seas.