Do sampans, fishing boats etc really communicate with enemy ships in the area? A recent set of events makes me think they do. I was to photo recon the anchorage at Rabaul, and was making my approach on the surface when I noticed I was passing a sampan just a couple thousand yards away. Two ships eventually converged in an area directly behind me and commenced depth charging. They did not rush there at full speed or anything, but definitely diverted to get there. In the end it worked out pretty well to have them behind me though.
Second, does the AI sonar only detect your sub when it is submerged? I was sneaking around a patrolling unit just SW of Peleliu on an extremely dark night. Overcast with 7knot winds and no moon. It was creeping along at 5 kts roughly westward, and I could not even hear it on sonar (although my sonar guy would report its bearings). I got right in front of him and slowed to about 3kts, slowly letting it close range so I could at least see it. The watch spotted it at about 4300yds, although I could see nothing through the TBT. Anyway, ID'd it as a Mutsuki DD, and slowly started to angle off it's course to open up some distance. I did not want to go too fast and create much of a bow wave, and I realized I was in a bit of a pickle, too close to get away, I was going to be run down. So I ordered a dive. As soon as I got below, the DD sped up and went right over top of me. He did not ping or drop any DC's, but he definitely seemed spooked about something in my area. It seemed to me that diving was what got me noticed.