Killface wrote:No movement was made after disembark.
Double walls wouldn't help against a "leave" range like this.
It seems that the reason you were thrown such a great distance is because the angle at which it tried to leave was filled with wall for all of that distance. Double layering should work as there would be an empty gap between the two walls where you could disembark, and you'd become trapped between the two layers of wall.
Having said that, the problem is also solved if you just leave a gap between your palisade and the water, where they can disembark rather than teleporting through the wall.