Winter can be fun. People who live near a small lake or pond can go ice skating. Most of the time, ice skating on a pond or lake is safe. But sometime it is not. The ice on the lake only looks solid. One of the things to watch out for is a dark patch under the ice . This may not be a safe spot. the dark patches are decaying plant matter. The ice will not be safe here . Decaying plant matter makes heat. Sometimes there is enough heat to melt the ice. These patches are not solid. they will break easily. If you try to skate on them, you could fall through the ice.