Embarking.

[Robert]

In previous civ games intercontinental warfare was rare. It took way too much time to get huge armies across an ocean, it was too expensive and required to much coordination and planning. With embarking in this is all gone! We can have inter continental wars, and having naval forces is finally important as well.

[MarinoCorps]

Here is another major Reason I think Civ 5 ruined strategy rather than enhanced it. In many games I actually care about "suspension of disbelief"... that any unit can suddenly magically transform it self into a boat that is capable of crossing oceans is ridiculous. One of the motivators for building a Navy at all was to be able to escort your transports to their destination. CIV IV had a lot of failings with it's AI and the successful implementation of Naval strategies was one of them. Civ 5 vanilla made a (IMO) retarded decision here... and making these units UNSTACKABLE and INDEFENSIBLE on the water was one of the dumbest design errors I have ever seen in this franchise that I love. GK improved on this error only slightly, as at least now an embarked Death Robot isn't immediately killed when attacked by a barbarian trireme. How any designer could defend that is beyond my capability for understanding.