The main purpose of an ocean liner is to get passengers from point A to point B in as fast a time as possible, and for this reason they have bigger and more powerful engines than cruise ships. The top speed of Queen Mary 2 is 29.62 knots, with a cruising speed of 26 knots. This compares with cruising speeds of modern cruise ships, such as Oasis of the Seas, of 22.6 knots.
Ocean liners are more likely to meet rough seas and unfavorable conditions which can be encountered in the middle of the ocean. They are therefore strongly built, with sturdier and thicker plating and a higher freeboard to withstand those conditions. They also carry more fuel and have larger storage facilities for victuals and other stores that they require on long passages. Cruise ships generally operate in calmer waters and make frequent stops, where they can replenish stores.
The voyage and its amenities are part of the experience offered to passengers on a modern cruise ship. Some of the amenities offered on cruise ships include buffet restaurants and fast food outlets -- some of which are open 24/7, a gym and fitness center, a Broadway-style theater, a casino, shops, a cinema, swimming pools, lounges, a library, a spa and hot tubs in many of the cabins. An ocean liner may have a few of these amenities, but most cruise ships have all of them.
Because of the extra weight that accompanies their more robust build, ocean liners have a much larger draught than do cruise ships. As a direct result of this, ocean liners are physically unable to visit many ports during their voyage. Many cruise ships offer cruises throughout the Caribbean, but an ocean liner would be unable to attempt such a cruise since their draught is far too large for the majority of Caribbean ports.
