kalarhan 说:
VC uses both systems for sea. Free travel (go anywhere with sea water), just like in land; on-rails travel (uses the bridge terrain to create a path on the water, but that is actually land).
That is pretty much it. Let me elaborate a bit further on the "on-rails travel" on rt_bridge: it is just a "bait" for the AI. As soon as they touch the bait (rt_bridge) they will be transformed into a party that can perform free travel on the sea. So the AI expects it to be a "on-rails travel" as long as they are on land, but as soon as they are on water, nobody will use the rails. The rails are a illusion.
The problem is that the party that takes the player captive does not adhere to the rails, but rather goes all over the place at it pleases them (it?) even on terrain that should be unpassable.
passable terrains for a party with the pf_is_ship flag are: rt_water, rt_river and rt_bridge
The party that takes the player captive does not need rt_bridge at all. rt_bridge is only the bait to get the land AI parties in the water.