In April 1992, in a gallery called "Mina" running along northern boundary of Wieliczka Salt Mine deposits, water leakage, previously small, increased instantly. The flow rate was about 5.000 liters per minute, reaching even 10.000 liters per minute. After a month the leakage decreased to the previous rate, but in mid-September it increased again, making its way through the salt deposit and washing out chambers. A considerable deformation of land surface was caused threatening the monastery. The authors present the course by the leakage, discuss reasons and deformation consequences.