Was doing a commercial gear survey and we flew over Dabob at about 100'. The lights were on so we knew a sub was practicing torpedoes. So, we went looking for it. Finally found this telephone pole (periscope) going down the center of the bay. Bright sunny day. Looking straight down we saw nothing. It was obviously right below the periscope and totally invisible.

Couple times those subs transited open gill net fisheries. Submerged. Kinda decorated the sail with nets.