I was listening to one of my favourite podcasts over the weekend, the Sinica Popup Chinese Podcast and they had a segment about a British submarine that sunk in the 1930s off China. While the podcast covers a wide range of subjects it was not a topic that I expected to hear. HMS Poseidon was a Parthian Class submarine that was launched just under two years prior to its loss on 9 June 1931. There was nothing particularly suspicious about its loss, it struck a Chinese freighter while training off Weihai in China where the Royal Navy still had a presence through a leasing arrangement with China. While tragic, the accident was marked as probably the first use of the Davis Submerged Escape Apparatus.