Or, why you can glide on skates. Water has a very novel phase diagram in that increased pressure on the solid form of water (ice) can force the substance to melt. (In many substances, the application of pressure would lead to solidification or freezing.) Ice skates concentrate the weight of a skater onto a very small area of metal in contact with the ice surface. Since pressure is the force (here, the weight of the skater) per unit area, the result is relatively high pressure immediately underneath the skate's blade. A thin layer of melted ice (water) forms, and this is what allows a skate to glide on ice. Note that the temperature of the ice/water has not changed. The effect is not due to friction. (If there were friction, you wouldn't glide.)

I now realise that this refers to why does ice float?. But i like this write-up, too.