The cramped sleeping arrangements on HMS Triumph
30 July 2012 Last updated at 08:00 BST
Able Seaman Chris Davies shows the confined living quarters aboard HMS Triumph with some crew having to share bunks no bigger than a coffin.
HMS Triumph is one of the Royal Navy's Trafalgar class submarines, using its stealth on counter-piracy, anti-terrorism and narcotics operations.
For the crew of 120 on HMS Triumph it has been an endurance challenge.