Have you seen the following simulation:
[url=http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=140.0]Relative Motion (frame of reference)[/url] and [url=http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=2125.0]Cross a river with a boat[/url]

I will think about it and try to create one according to your need!