There are many ducklings on the water at Swanshurst Park, some tiny, some this size. The duck and duckling shown here are mallards.
You're probably quite familiar with the mallard as it's very common, but just in case you're not, here's some information.
Mallards are widespead and very common throughout the UK. The male has a dark green head, a yellow beak, is mainly purple-brown on the breast and grey on the body. The female is mainly brown with an orange bill. Mallards eat seeds, acorns, berries, plants, insects and shellfish.