UK technical diving instructor-trainer Will Goodman has claimed a record dive to 290m using an unmodified JJ closed-circuit rebreather.
Goodman reported that his computers stopped registering at 290m, but estimates that his actual depth exceeded 300m.
Goodman, who runs Goodwilldiving at Lombok, Indonesia and was previously recognised as Guinness World Record-holder for the longest scuba dive, carried out the JJ-CCR dive at Lombok in late March, following a year's training and preparation.
The diver surfaced after nine hours and 57 minutes, showing no signs of decompression illness or dehydration.
"It was the toughest and most challenging environment I have ever been in," he said. "I reached the bottom after a nine-minute freefall in absolute darkness. Water temperature at depth was 10° and a strong current was running.
"I had high narcosis due to the nitrogen levels in my breathing mix, and HPNS (whole body tremors) from the amount of helium in the mix contributed to by the rapid descent rate.
"My hands started shaking and, on ascent, I wondered if I'd make it back, as I began to lose my motor function.
"I can't thank the team enough for this amazing opportunity and all their hard work," Goodman added.
Although not recognised as an official Guinness World Record, because Guinness has no CCR depth-record category, Goodman can claim to have bettered a previous depth record of 283m set by Krzysztof Starnawski.