Mojang removed the boat controls and replaced it with the horse controls to make things cleaner. However, I can confirm that the boat is UNSTEERABLE... you are unable to turn unless moving forward, and the brakes on the boats fail every time, meaning every time you want to stop, you must wait for the boat to slow down, or crash it into the shore.
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Perhaps you mean it is what Mojang intended, but it is not how boats "should" work. Right now there is no way to slow down or make sharper turns. This is not how a rowboat (which is what we have in Minecraft) actually works. If I'm going at speed and put both oars in the water, I slow down.. If I dip the right oar, I turn right, left oar, turn left...
If you don't like the current intended boat behaviour, please suggest a better one on the Minecraft Forums: Suggestions.
Also if they wanted to make this that realistic... you'd have to craft oars with your boat. Open the boat "inventory" while on it and place the oars in. Then radnomly while your going an oar would fall off and float mear inches from your reach making you pull out a stick and hit the water until it miraculously came back to you. All the while zombies and skeletons would spawn on shoar laughing at you because of your perdiciment.
Granted I'm not thrilled with the mechanics either but like Tails said... you should post this on the sugestion forums.
Probably would get more attention on reddit, I doubt Mojang even goes to minecraftforums

@unknown has repeatedly mentioned the minecraft suggestions subreddit.
Duplicate of MC-14521, please use the search function to see if your bug has already been submitted. Currently over 57% of tickets are being closed as duplicate.