Divers in north Norfolk had the chance to use a specialist piece of equipment, used to explore the deepest waters.
They practised on a 'rebreather', which retains the user's exhaled breath, absorbs the carbon dioxide and reuses the oxygen, so extending the duration of the dive.
The rebreather was brought along to North Norfolk Divers' Club meeting by Dave Lock, The British Sub-Aqua Club's national diving and coaching group leader and chief technical training officer.
North Norfolk members have been trained to dive using the conventional 'open circuit' method, and are also used to seeing bubbles when they exhale, something which does not happen with the rebreather.
Most scuba divers, using open circuit equipment, can only achieve a maximum depth of 50m.
Mr Lock had used a rebreather when exploring HMS Victoria, which was accidently rammed and sunk off Tripoli in June 1893 by the battleship HMS Camperdown, with the loss of 358 crew.
She is the world's only vertical wreck and, as she lies in 150m - the stern being the shallowest part at 76m - is considered a highly-technical dive,
At one time rebreathers were only available to the Navy but the equipment is now becoming more widely used, although it requires extensive training by qualified technical instructors.
Club members meet on Thursdays at The Feathers, Holt, and train in the swimming pool at Gresham's School in the town.
They have their own boat, launching from Weybourne, and dive up to 25 miles offshore.
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