Swimming in a sea of ice needles is probably not everyone's idea of leisure, but these divers decided to plough their way through them in Lake Baikal, Siberia.

Lake Baikal in south-east Siberia is the world's oldest and deepest lake. While winter might now be over, it is during this time of the year that this unusual icy phenomenon can be seen.

The ice needles form in calm waters, as the crystals grow horizontally across the surface of the water. They continue to grow until they run into each other and stick together, filling the remainder of the water between until it becomes a solid sheet.

In spring, the sun starts to warm the ice sheet. This weakens the bond between the crystals, causing the ice to break up into the individual needle elements once again.

Although nearly two metres thick, the ice sheet will shatter if you step on it as it weakens, so can be immensely dangerous.

Have you ever seen anything like this before? Send in your rare wintry phenomena to our dedicated uploader if so... and don't try this at home!