HMS Syrtis
... that the British submarine HMS Syrtis twice towed X-class midget submarines, and on both occasions the submarines sank while under tow?
... that the British submarine <b id="mwBYM"><a href="./HMS_Syrtis" id="mwBYQ" rel="mw:WikiLink" title="HMS Syrtis">HMS <i id="mwBYU">Syrtis</i></a></b> twice towed <a href="./X-class_submarine" id="mwBYY" rel="mw:WikiLink" title="X-class submarine">X-class</a> <a href="./Midget_submarine" id="mwBYc" rel="mw:WikiLink" title="Midget submarine">midget submarines</a>, and on both occasions the submarines sank while under tow?