Imagine being in your garden, hanging out some washing, when the ground suddenly drops away from under your feet.
That's exactly what happened to a woman in Melbourne this week, when a sinkhole three metres deep opened up beneath her while she was doing chores.
A neighbour heard the 45-year-old screaming for help and called rescuers.
Firefighters then managed to pull the woman out of the hole, which had partially filled with water.
Amazingly she was unharmed by her fall but told medical staff that she had to tread water for 20 minutes while waiting for help.
"The issue is the hole in the ground is only 500 (centimetres) wide but it actually opens up very big inside so there was nothing for her to grab onto to try and get herself out," explained local fire official Paul Carrigg.
"Every time she put her hands up, the dirt disappeared. So, there was nothing she could do to help herself.
"She's extremely lucky person, there's no doubt about that."
Local council engineers blamed an old well for the collapse.
Sinkholes, or dolines, often take thousands of years to form and vary hugely in size.
The deepest is China's Xiaozhai Tienkeng at 2172ft (662m). The Qattara Depression in Egypt is roughly 50 miles (80km) by 75 miles (121km) in surface size.
But often sinkholes can be only a few metres in diameter.
They are often caused by acidic water dissolving a layer of rock underneath the ground.