HMS Thetis was an Apollo 2nd class protected cruiser launched on December 13 1890. The latter half of her career was spent as a mine-layer. She was deliberately sunk in attempt to block the canal at Zeebrugge during the First World War, on April 23, 1918.
The Group 1 T Class submarine HMS Thetis was built by Cammell Laird in Liverpool, England and launched on June 29 1938. Trials were delayed because the forward hydroplanes jammed, but eventually started in Liverpool Bay under Lieutenant-Commander G. Bolus. The first dive was attempted on June 1, 1939 at about 2 pm.
The submarine was too light to dive, so a survey of the water in the various tanks on board was made. One of the checks was whether the internal torpedo tubes were flooded.
Lieutenant Frederick Woods, the torpedo officer, opened the test cocks on the tubes. Unfortunately, the test cock on tube number 5 was blocked by some enamel paint and so no water flowed out even though the bow cap was open. This combined with a confusing layout of the bow cap indicators - they were arranged in a vertical line with 5 at the bottom - 1,2,3,4,6, and then 5; and the shut position for tube 5 on the dial was in a different position to the other torpedo tubes - led to the inner door of the tube being opened. The inrush of water caused the bow of the submarine to sink to the seabed 150 feet below the surface.
Although the stern remained on the surface, only four crew 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. As well as the normal crew of 53, there were 26 Cammell Laird employees, 9 further naval officers, 4 Vickers Armstrong employees and 2 caterers. The crew waited before abandoning the vessel until it had been discovered by HMS Brazen, a destroyer which had been sent to search for it and which indicated her presence by dropping small explosive charges into the water.
The submarine was subsequently salvaged and repaired, being commissioned as HMS Thunderbolt. The torpedo tubes on British submarines are equipped with a Thetis clip, one of the modifications introduced as a result of the accident. This is a latch which allows a torpedo tube door to be opened a small amount in case it is open to the sea at the bow end. Once it is clear that no flooding will occur the latch can be released and the door fully opened.General Characteristics