Artur Kozlowski reached 103 metres (338ft) below ground in the Pollatoomary cave in south Mayo last month. This surpasses the previous British/Irish record of 90 metres attributed to Britain's deepest cave, Wookey Hole, in the Mendip hill in Somerset.
Leading British cave explorer, or speleologist, Martyn Farr has paid tribute to Mr Kozlowski's "very exciting achievement", which was undertaken with the support of fellow speleologist Tom Malone.
The Pollatoomary discovery establishes once again that Ireland has some of the finest subterranean caves in western Europe, Mr Farr said. Pollatoomary had been located initially by Mr Farr in 1978 close to the Aille river, which rises in Mayo's Partry mountains.
The river runs underground some 10km southeast of Westport, and reappears three kilometres further on at Bellaburke where the underground cavern is located.
Mr Farr reached a depth of 33 metres at that stage, and believed this to be the cave floor. "Obviously it was just a ledge," he said yesterday .
Mr Kozlowski, who was trained by Mr Farr, explored the area in May of this year. Initially, he recorded a depth of 86 metres, swimming in cramped confines in poor visibility through the Pollatoomary cavern.
In July, he returned with Tom Malone and tied off his line at a depth of 103 metres after a three-hour dive, using a "trimix" mixture of gases to avoid the "bends".
Describing it as his "journey to the centre of the earth", Mr Kozlowski said that some "uncomfortably constricting" and "occasionally tight" sections of the cave opened up into a passage beyond 70 metres, which dropped further at a 35 to 40 degree angle.
He dropped to 103 metres, as confirmed on his two depth gauges, before ascending slowly to the "world of light".
"Cave diving is completely different from ocean diving, in that you can't just float gracefully down," Mr Farr explained.
"There's an awful lot of wriggling in tight corners. It really can only be compared to space exploration, in that we have climbed the world's highest mountains, explored parts of the ocean, but the subterranean is the last frontier."
Life forms do exist at these depths, he said. "Imagine when you are swimming along, or negotiating very tight spaces, and suddenly an eel careers into your mask, jaws open and eyes piercing. The eel is harmless, but the effect when you are concentrating is pretty electric," he said.
Siggins, Lorna. Irish Times [Dublin] 07 Aug 2008