Teal are the smallest of the dabbling ducks, which may dabble on the water or ‘upend’ to get at things below (as opposed to divers). According to WWT Slimbridge, “Dabbling ducks legs are further central than other types of duck enabling them to walk well on land and graze. Dabbling ducks tend to take flight when spooked or on the move and are able to take flight straight from the water, unlike divers which have to run across the water to gain momentum.”
Some teal are resident in the UK, and many over-winter here, which this one might be is not clear to me.
This bird is of course the origin of the name of the colour teal.