HMS H29 was an H Class submarine built by Vickers at Barrow-in-Furness. She was laid down in March 1917 and commissioned in September 1918. On 9 August 1926 she was conducting trails on her torpedo discharge system in 2 Basin at Devonport. The trial required the boat to trim down aft. During this evolution the water level rose over the engine room hatch which was fouled by some pipework and the boat sank taking the lives of the Chief ERA and five dockyard workers.
The wreck was raised and sold for scrap in October 1927.