What do Swans eat?

Well thats a very fine question and to this day I still dunno..but i do know they eat something from under these lillies.

+Christopher Prins , you are very lucky to live so close to the Cattai Wetlands, this is an amazing location which i am sure I could come back again and again.

View large to find out what this swan is really doing.(maybe just ducking under water to avoid the mozzies and bees?)