The complete defence system for Manila Bay shown below as per the diagram in the prior post.
2 minefields stretching across the bay and 1 subnet at the top left protecting the dry dock.
There is a gap in the lower minefield for the larger allied ships to pass through...this passage defended by 2 frigates. All AI ships will have waypoints taking them safely past the mine field.
With these missions based in Manila I recommend the challenge of taking your sub through the minefield...... but you can always skirt around it if you keep getting blown up.
I am looking for buoys for Sh4 but do not think these are available.