DRAMATIC footage has revealed how casualties are dealt with under the waves onboard a nuclear submarine.

British cameras were allowed on a hunter-killer submarine for the first time in Channel 5 documentary Submarine: Life Under the Waves.

The docu-series lifts the lid on live onboard the Barrow-built HMS Trenchant, a 5,300 tonne Trafalgar class submarine.

‘Casualty, casualty, casualty!’ is announced from one of the intercom speakers on board HMS Trenchant before crewmates are seen scrambling to get first aid supplies to the right area of the vessel.

The crew member has to be evacuated in the middle of the Atlantic, forcing the submarine to surface even though rough seas make removing him from the boat extremely dangerous.

The two-part documentary series focuses on a four month tour of duty to the mid-Atlantic as the boat protects another sub carrying a Trident missile.

The series shows how the crew are forced to live in extremely close quarters while helping to keep British waters safe.

The Trafalgar-class nuclear-powered submarine was launched by war hero Vice Admiral Sir Arthur Hezlet – commander of the original HMS Trenchant submarine during the Second World War.

The boat sailed home for the final time earlier this year ahead of being decommissioned.

The documentary comes following the BBC thriller Vigil, set on a Vanguard-class Trident submarine, which has been criticised for its inaccuracies.

A description of the show aid: “For the first time British cameras have been given access on board a hunter-killer submarine on live operations.

“Living in extremely close quarters the crew are tasked with helping guard the UK’s Trident missiles and keeping British waters safe.”

The next part of the programme airs at 9pm on Monday.