Two cave divers have set a new British depth record at Wookey Hole Caves in Somerset.
The pair developed their own breathing apparatus
Rick Stanton and John Volanthen went more than a mile into caverns, clearing gravel and rock in their way before reaching a depth of 76m.
The previous record of 71m was set in Speedwell Cavern in Derbyshire in 2003.
"We wear a computer which shows us the depth," said Mr Stanton. "We both have records that show our depth was 76 metres."
"If you compare us to mountain climbers - even an unclimbed peak - they know everything about it," he added.
"Even when they went to the moon, they had a map and knew everything that would surround them.
"Yet here we have no idea what's going to happen around the next bend."
Mr Stanton, a 43-year-old firefighter from Coventry, was involved in the rescue of 13 British cavers in Mexico earlier this year.
Together with Mr Volanthen, a 33-year-old Bristol-based engineer, the pair developed a "rebreather" unit to allow them to stay underwater for longer periods.