Thanks for this thread, you makes me wonder about, then test
On barrier patrols, subs will go from the initial point to the barrier point, come back and restart same process indefinitly.
If you put more than one barrier WP, they will be ignored.
During that time, with a (presumed because never the same) random factor, the sub will come back 5 mn to shallow depth (to transmit data with wire antenna) and after this 5 minutes, will dive again to programmed depth until the next SD event.
I just measured it, on some tests, in accelerate time :
the first PD occurs beetween 1h and 1h50 and you must wait ~4 hours for the second.
So I find this very interesting to use !
you just have to put a simple barrier point, and the AI sub will do the job and even manage to jump on the link, regularly, during 5 minutes only, to transmit or receive data
Coupled with other platforms, this allow the sub in barrier tactic to have a very good situational awarness.
If you want to avoid the sub to go in shallow depth, use area weapons instead of barrier.
delete one WP and put the sub beetween the last 2 WP => you have a barrier tactic ...