As lovers of both water and winter, we spend a lot of time researching and writing about how to tell if a frozen lake is safe to walk on. The standard advice is simple: make sure ice is at least 20 centimetres thick, look for a clear blue colour, and avoid ice that has flowing water nearby.
After watching the above video, perhaps we should add that chipping away at a frozen lake with a golf club is a surefire way to test not only the ice, but the water temperature beneath.