The table must be clean, not greasy. You probably want to prop it up by about 6-12 centimetres if it is 1.5 m long. But you will have to experiment with this.

Add some blue food colouring or ink to a jug of water. This is your source of river water.

The next part needs care and practice, so don't give up if it doesn't work at first. Pour the water very slowly and evenly from the jug so that it runs down the table from the very top. The idea is to pour just enough water to keep a stream flowing, but not too much or the meanders will be washed out.

While one person does the pouring, others can watch the snaking water. They should be able to see that the water is deeper on the outside of the bend than the inside and that the meanders keep changing position, moving down the table.