Go outside when it is dry on the ground with a bucket of water and a paint brush or roller, a spray bottle or an old washing up liquid bottle filled with water or anything else that might spread water over a surface.
Your challenge is to make pictures, write words (or sentences if you're quick enough), make shapes, or leave a message. Paint, spray and roll water on to walls, pavements and any other surface you can find. Make sure you use plenty of water so your masterpieces can be seen clearly and will survive long enough to take a photograph - we'd love to see them.
What happens to your graffiti? Why?