The following was sent to us via email: In a lake, there are lots of hydrophytes. But their pattern seems to change every now and then. For example, every day in the morning, these plants are spread across throughout the lake. But the same evening they move towards one corner of the lake and the rest of the lake is clear. It is the same routine I've watched for about 15days now. Why does this happen? Is there any phenomenon behind this behaviour of the water plants?