A woman was hanging the laundry in her Melbourne, Australia backyard when she fell down a 3m deep sinkhole that suddenly opened up, it was reported on Tuesday. The 45-year-old woman fell into an underground water cave and was trapped for more than 20 minutes before a neighbour heard her cries for help and called police, the ABC broadcaster reported. Ambulance official Stephanie Palamberis said the woman was underwater at one stage but managed to swim up and keep her head above water. Fire-fighters got a rope to her and pulled her out.”This was a very unusual incident”, fire operations officer Paul Carrig said. “Fortunately, the lady escaped without injury though she was obviously shaken up. She’s a very lucky lady.” He said the sinkhole appeared to be caused by a burst water pipe.