In curling, the drops of frozen water that create a raised surface on top of the ice sheet for the curling rocks to run on. The pebble is susceptible to wear as the rocks run on it and the temperature fluctuates, causing the curling conditions to change. Curlers are forbidden to touch the ice surface with a bare hand (or a bare anything, for that matter) lest body heat melt the pebble.
Between games, the old pebble is scraped away, and then fresh pebble is sprinkled on the ice surface. This is usually by a rink employee with a back-mounted water pack and a spray hose.