Autorotation to tween gameobject

Ola!

Just started to work with unity and created a nice landscape with a kickass speedboat. Working on the TweenPath for the boatride and can't get my head around how to make the boat autorotate to the direction it's heading.

LookAt could do the trick with an object heading down the same path just in front of my boat. But there has to be a more delicate way... right? Other option might be to read and compare xyz each frame en calc a direction it's going in, perhaps anyone has tips for that?

Thanks in advance, J