I know he spent some time on some ships where he described firing depth charges off the side after submarines in the Indian Ocean. Though, he never sunk/saw a submarine. I am not sure that this "service record" is correct, as it is specifically extracted from his "Pay and Victuals" which I believe is just a record of where he was when he got his payments - There appears not to be a detailed service record, only where he was stationed at the time of his pay. So I suspect he was out and about on various duties on the sea in between. Maybe he worked on the Walrus Aircraft? That fits Submarine hunting - As for the Shaw and Begum, he may have been attached to a training Squadron, and as you say, brought onboard to work on various damaged craft.