Ok, so its a little late in ArmA-1 life to discover this, but its a pretty significant bug.
Seems near all user made custom island/terrain stops all (AI) large ship movement in its tracks!
Not small boats, just ships, typically anything longer than 20 meters.
Probably many factors involved, but on Sahrani (snd BIS islands) theres no problems.
One factor seems to be Binarizing the island addon.
I've been working on my Water World map and didn't have any problems with ship movement until either/or a) messed with the layer texture and b) binarized it.
I changed BinPBO to preserver all files just in case that was the problem, didnt help, so it seems that the binarized WRP file cause it.
The underwater texture does effect vehicle speed, but this is not so much speed problem, it simply large ships will not move AT ALL.
Gardinas island is one of the few user made addons that doesnt have the problem, but I suspect its because its not Binarized.
How can I prove if the wrp file is Binarized?
Maybe its the seabed texture BIS use ..... I can only hope, but how do I get the exact layer and texture info ..... ?
........ any comments, suggestions or answers on this weird arse problem gratefully accepted !