Just watched a documentary on U18 one of the last of the 206A class which was scrapped late last year. Unfortunately I did not see all of the programme, but 2 things interested me in particular. The Captain commented on the activities of porpoises, which apparently have a liking for submarines and try to talk to them, they are so talkative and loud that they interfere with the boats primary task of int gathering and stalking of anything and everthing that floats on the surface. The second item was stalking a USN carrier, which was completely unaware of the uninvited attention, they took a photo through the periscope which was later published, apparently the USN Captain was looking for another job shortly after. The Chinese are not the only ones who lurk where they are not wanted.