Boats do not work in 13w16a

You can use the boat but it will stuck all the time by a delay of a few seconds.
I made a video for the demostration that you can use but it stucks all the time.
http://www.youtube.com/watch?v=uQDnLMM7VKc

Reposting my comment for MC-13751 here for the fact that it covers more information on the root of the problem.

It appears to be that the boat is not syncing it's position correctly, resulting in the behavior everyone is seeing. Try sailing a boat a ways away from where you got in, and get out using lshift (as trying to activate it will result in you shifting out and back in again). You will teleport back to where you got in. It seems the riding mechanic was updated, but they forgot about the boat. Obviously, horses work, and I tested minecarts to be in working order, but even testing by way of a waterslide with the boat yields instant teleportation to the starting position in my testing. Of course, in this state since the boat isn't actually moving, it is entirely unbreakable, and if you teleport back to start you can't access the boat at the bottom because it's essentially a ghost. Reload the world however, and the boat is back where it was when you got in. I have not tested with a server and two local clients, but it seems that from this if one user gets in a boat while the other is watching, to the observer the boat would not move at all. This should be tested.

Confirmed.

I'm seeing boats consistently cause null pointer exceptions on all clients in SMP.

That's a different issue, reported here: MC-13704.

In 13w24b the keys don't steer the boat

That's MC-14521.

This is still a problem in 14w17a. Boats go hardly anywhere. It seems like they go somewhere, but when you get out you're many blocks away. Watching someone else ride in a boat makes it look like they're going, but then they keep glitching back.