Young children sometimes play in puddles of mud. Mud is usually brown. Some animals including worms, frogs, snails, clams, and crayfish live in mud. Pigs and elephants use it to cool themselves in hot weather. Some people enjoy making mud pies out of mud.
Great river systems like the Amazon bring down to the delta immense amounts of mud which ends up in the sea outside the fan of the river mouth. Mudrock is what the mud may become millions of years later. Mudrocks make up fifty percent of the sedimentary rocks in the geologic record, and are easily the most widespread deposits on Earth.