I'm pretty sure phoenixc said the other worlds were OK. I would try a fresh game of IP.
Just load the game, go to the main menu and start a new IP game, phoenixc.
I tried.... I believe skadi is right .... If routing has to do with the continuity of the animation then it means that it is the IP town fault.
Using doesn't mather what boats on a custom world, the moving has continuity.... all the sim animation has continuity...
By the way, my boats never did go on the field or on the road...
Conclusion: Island Paradise disappointed me with animation parameters.
Have you tried removing the school/sports arena and replacing it with two separate buildings? Apparently that building is causing a whole lot of problems and some of the problems clear up when the building is deleted and two new buildings added. Of course the routing issues aren't solve, but it might help with the animation.