Hi Dave, do you remember roughly when this was? The reason I ask is because a Chatham-built submarine, HMS Tradewind, was used as the prototype for a conversion into a high speed submarine. The conversion was covered in the article about HMS Tradewind on the old forum, but I haven't managed to retrieve it yet.
The data gathered from those trials was used to design the later conversions for Second World War-built submarines of the T and A Classes and in the designs for the 50s and 60s-built submarines of the Porpoise and Oberon Classes.
The designs they produced were slightly faster surfaced than dived. The boats which are faster dived are of the slightly more modern teardrop or cylindrical shape, the first of which was actually the American boat USS Albacore. All modern submarines are of this kind of shape now, particularly nuclear-powered boats.
It was actually the Germans who designed the first proper submarines. Before the advent of the German Type XXI and XXIII U-Boats towards the end of the Second World War, submarines were little more than submersible Torpedo boats, whereas the German boats were designed to operate submerged all the time, only coming up to periscope depth to raise their snorkel and run their diesel engines to draw fresh air into the boat and recharge their batteries every couple of days.
The conversion of HMS Tradewind was prompted by the capture at the end of the war of some of these German boats which the Allies found were far superior to their own submarines.