I drove my boat onto the shore by accident and thought I was stuck, it didn't come to mind the whole game is based on physics. Getting out of the boat and gently pushing it by running against the hull solved the problem.

You can even move the boat in the water to a different direction. Jump off and swim against one side to turn it around.

This is not as obvious as someone might think :)

Like here: http://i.imgur.com/2o0DxRx.jpg