Mallards are normally known as Dabbling Ducks, but they do dive occasionally if the food is available.
The other day I was watching some Mallards from a bridge and they were diving in some 2 metres of water. They would mingle around (Male and Female) and suddenly make a considerable splash as they dived forcefully down to the bottom.
This went on for some time and after every third or fourth dive they would shake the water from their wings and then continue to dive.
I noticed that on most occasions after surfacing they would be eating something they had collected from the bottom. It appeared to be some form of Molluscs (small shells) and as you can see from the images below some where stuck together.
As a result of shaking the water from their wings this provides an opportunity to view the colourful iridescent speculum feathers on their wings.
The Mallard is one of the most widely distributed species of Duck across much of the World.
It exists in a wide range of habitat and climate and eats a wide variety of food.