Problem setting: A man with a boat at point S at sea wants to get to point Q inland. Point S is distance d1 from the closest point P on the shore, point Q is distance d2 from the closest point T on the shore and point P and T are at a distance of d.
Question: If the man rows with a speed of vr and walks with a speed of vw at what point R should he beach the boat in order to get from point S to point Q in the least possible time?
To use: Click and drag input parameters to desired values. Then click - don't drag - the slider point 
for R (you need to see the point glow 
). Then you can use arrow keys to find minimum Time.