Automatic Boat Script

[Bearded Munro]

I'm looking for a basic script to allow a boat to sail continually and automatically around a number of sims. I know these scripts have existed for ages, and there are plenty of trolley bus and train scripts about. I have a guided tour maker, but I want this to run whether there are people on board or not. Even better would be a script that would rez a vessel on the edge of a sim, sail it across and off the other side. I have seen this on sims previously but now I can't find anything vaguely resembling  it; there are plenty of tours and vehicles that rez for guests, but not vehicles, in this case ships, that just travel automatically. 

(I own a gorean RP sim part of a cluster, and it would be great to have some merchant ships sailing around...)

Any help would be great appreciated.