Experience, mostly. Sounds of the cracking ice tell you a lot. You can get more sounds with a stick hitting the ice. Also if you can't make a hole with the stick, you won't fall through. But we're prepared to fall in the water, it happens, but we know how to get back on the ice. So no, we're not afraid :)

@@ondrejsindelar Thank you very much for your reply. From what I've seen of people skating on frozen water, sometimes the flow of water underneath looks very fast and I can only imagine that being problematic when someone falls in. Regardless of those issues, appreciate seeing another world and experiencing it from afar.

As a Dutch and therefor iceskaterfanatic....yes it is kindof dangerous surely when it has just frozen and the ice is 5 cm or so. Sometimes you have places with more wind, that still are frozen but less than cm. Falling in without equipment can mean...death. And every winter it happens. If you go under ice of even 1,5 to 2 cm thick you cannot break it. You need to find the hole in the ice. So when the ice is 10 cm thick it is safe. But I rarely went out alone on my own, always with more people around.

@@lenorehoward7215 Ice rarely form under fast moving water. And it is not nice to skate on if it forms, not smooth. SO this is all on lakes and canals or very slow moving rivers mostly.

@@jaysimoes3705 thank you very much for such insights. Happy skating!

It was many different lakes, mostly east of Stockholm

Was it not west of Stockholm ( on lakes)?

sorry, west. not many lakes east of Stockholm :)