HMS Agamemnon Completes First Dive Ahead of Sea Trials

HMS Agamemnon completing her first underwater dive | Photo: Submarine Delivery Agency, UK Ministry of Defence

HMS Agamemnon, the sixth Astute Class submarine, has completed her first dive, marking a key step toward joining the Royal Navy’s operational fleet. The dive took place over two days at BAE Systems’ shipyard in Barrow-in-Furness, shortly after the vessel’s commissioning ceremony, which was attended by His Majesty the King.

According to the Ministry of Defence and the Submarine Delivery Agency, the first dive forms part of a submarine’s testing and commissioning process before it goes to sea for the first time. The activity included two main stages — a basin dive and a trim and inclining experiment — conducted by BAE Systems engineers and the ship’s crew under the supervision of MOD and SDA naval architects.

During the basin dive, onboard systems such as ballast tanks were tested to ensure the submarine’s ability to surface safely. In the trim and inclining experiment, 16 tonnes of lead weights were moved across the submarine to determine her centre of gravity. The test also used pendulums hung between decks — a method that has been employed in naval architecture for centuries — to assess stability and weight distribution. The Submarine Delivery Agency said in a tweet, “HMS Agamemnon’s onboard systems were tested. This included the ballast tanks which ensure she can surface. The vessel’s precise weight and centre of gravity were also established.”

The data from these tests will confirm the submarine’s stability and handling characteristics in preparation for sea trials. Once operational, HMS Agamemnon will join her five sister boats — Astute, Ambush, Artful, Audacious, and Anson — in service with the Royal Navy.

HMS Agamemnon was officially named in April 2024 and launched in October 2024. The submarine measures 97 metres in length, displaces 7,400 tonnes, and is part of the UK’s Astute Class of nuclear-powered attack submarines, which conduct intelligence, reconnaissance, and global operational support missions.