There's a reason sailing the sea in the GameCube version of The Legend of Zelda: The Wind Waker was so slow and tedious. If the boat moved any faster, you'd sail off the edge of the ocean. Flat-Earthers smell a conspiracy!
No, really, the GameCube didn't have the power necessary to render the entirety of Wind Waker's ocean all at once; it could do so only in chunks, and had to keep Link's skiff from sailing past what was in memory. As director Eiji Aonuma explains, that's not a problem with the Wii U's upgraded processing, which can load the entire ocean at once. Rather than subject players to sailing at the same snail's pace of the GameCube version, the Wind Waker HD remake will allow for faster travel.
The speed boost must be acquired, though. Even if Aonuma wanted people to be able to sail the vast sea more conveniently, he wanted them to appreciate its size at first.
Other upgrades in the HD version include touch screen controls for manipulating the Wind Waker baton. Aonuma also has a puzzling reaction to what high definition does for Wind Waker's cartoon presentation. "It's as if it has become more real now that it's in HD. Even though it's animated and not real, I think there's a a surreal sense of realism."
I kid. Seriously, I could watch Nintendo Developer Directs 24/7. They do a strong job of conveying their creators' vision, and aren't so exclusionary that they rely on your prior knowledge of a series to make a point. Enjoy.