The lake Divje jezero near Slovenian town of Idrija is well known among extreme cave divers. There were several attempts to dive as deep as possible into the sump and three people have already lost their lives. Until now the record of -136 meters belongs to the late Tomo Vrhovec, Oliver Isler with 122 meters has came very close. But Italian Luigi Casati with the assistance of his life long diving companion, well known Swiss Jean-Jaques Bolanz descended even deeper. In 25 minutes he got as deep as -160m on aprox 450m length into the sump. He used underwater scooter and many stage diving tanks, filled with air and trimix (breathing mixture of helium, oxygen and nitrogen). He had to spent 8 more hours decompressing the dissolved gases in his blood on the way back. Last 3 and half hours he spent in an underwater cage (bell) - filled with air and with telephone connection... all submerged in a cave. The main problem, as Luigi was explaining after, was poor visibility and extreme cold.

One can survive in 6 degrees Celsius water over such a long period of time only in a decompression bell with battery powered heating systems under the dry diving suit.