The 'Trim and Basin Dive', which took place in Devonshire Dock, Barrow, involved submerging Astute in a dive hole large enough for the 100M-long, 7,400 tonnes boat. The dive was the first time that the submarine had been fully submerged, and provided the opportunity to test the submarine's underwater stability and systems.
25 of her crew were on board, alongside BAE Systems technicians, to carry out the tests, including trials of various boat systems, equipment and the mechanism that releases an emergency buoy, the emergency escape tower, and various hydraulics and electrical systems.
Lord Drayson, Minister for Defence Equipment and Support, said:
"This is an important step on the road to preparing Astute for service. These submarines are hugely impressive vessels, and will provide the Royal Navy with a world class capability."
After completing the dive, Astute was taken back into Devonshire Dock Hall. The next stage will be to calculate her stability, weight and buoyancy.
Astute is the first nuclear submarine to be launched in the UK for almost a decade. She has been built in the UK using the latest and most advanced naval engineering techniques. Construction has been described as more complex than that of the space shuttle.
Astute was named on 8 June 2007 by HRH Duchess of Cornwall at the roll-out ceremony at BAE Systems' shipyard in Barrow, Cumbria. She will never need to be refuelled: her advanced on-board life support systems mean she can circumnavigate the globe without needing to surface.
Astute is the first vessel of four in the Astute class currently under build and commissioning at Barrow. The other three are Ambush, Artful and Audacious.