Alright, sorry Les, I don't know if this will be against forum rules or not. This company does not make any money nor ask for donations so I assume it should be ok. I found a docking simulator called BoatMaster. It is completely free and it's the only simulator I have ever found that you can control whether it has twins, singles, size of boat, etc. It actually teaches a general idea of what certain lines do while docking, such as how a boat will react when you use a spring line. Go to www.boatmaster.org. Once you download the version you can play with a demo where you can't change anything. Then, you e-mail the creator for a key that he/she gives you and then you can change anything you want. Like I said, I'm sorry if this is against board rules and remove this post if it is.