A demo of Water rangolis by Lakshmi, Rajamma, Akila and Asha:
Rangoli on water:
Required: a glass bowl, cold water, a couple of tablespoons of oil, rangoli powder.
Instructions:
Smear the oil on the bottom of a bowl and fill it with ice cold water - this way the rangoli will stay for a couple of days (or else just ordinary water would do with no oil coating and the rangoli will stay for a lesser time).
Use a tea strainer to sprinkle a thick coat of distemper on the water surface (you can use talcum powder or fine rice flour too).
You could create your rangoli on top of the distemper/talcum powder layer, on the bowl of water.
You can also mix colour in the distemper so that the base is coloured and draw kolam with white kolapodi on top to give it a different effect.