of water caused the bow of the submarine to sink to the seabed below the surface. How the outer door (bow cap) to Tube 5 became open to the sea is unknown: Woods maintained that until at least 10 minutes before he opened the tube all the indicators were at "Shut". An indicator buoy was released and smoke candle fired. By 16:00, Grebe Cock was becoming concerned for the safety of Thetis and radioed HMS Dolphin submarine base at Gosport. A search was immediately instigated. Although the stern remained on the surface, only three RN personnel (Lieutenant Frederick Woods, Captain Harry Oram and Leading Stoker Walter Arnold) and one Cammell Laird man (Fitter Frank Shaw) escaped before the rest were overcome by carbon dioxide poisoning caused by the crowded conditions, the increased atmospheric pressure and a delay of 20 hours before the evacuation started. Ninety-nine lives were lost in the incident: 51 crew members, 26 Cammell Laird employees, 8 other naval officers, 7 Admiralty overseeing officers, 4 Vickers-Armstrong employees, 2 caterers and a Mersey pilot. The crew waited before abandoning the vessel until she had been discovered by the destroyer , which had been sent to search for her and which indicated her presence by dropping small explosive charges into the water. In order to effect an escape from the stricken vessel, the escaping crew were required to enter the submarine's only escape chamber, which could only accommodate one person at a time. As the pressure outside the submarine was greater than the pressure inside, this had to be equalised before the outer door of the escape chamber was opened. The escape chamber was flooded with the occupant having to wait until the chamber was completely full of water. Only then would the pressure within the escape chamber be equal to the outside sea pressure. In the case of HMS Thetis, four members of the ship's company, three RN personnel (Lieutenant Woods, Captain Oram and Leading Stoker Arnold) and one Cammell Laird's employee (Fitter Shaw) successfully used the escape chamber. During the fifth attempt to escape the occupant of the chamber panicked and tried to open the outer escape hatch before the chamber had completely flooded. As a result, the increased pressure outside the submarine caused an in-rush of sea water, thus drowning the escapee. Because the outer escape hatch remained partially open it rendered the escape chamber inoperative, preventing