The Moorhen (Gallinula Chloropus) is a member of the rail family and the most obvious ID features are the red frontal shield with its waxy yellow tip, just as if it has been dipped in poster paint; a broken white line separating the wings from the belly.....
and not least (often the most common view FOR ME) the predominant white sides to the undertail.
It often looks as if it is making heavy weather when swimming with the exaggerated nodding of it head in time with the stroke of its feet just like a cyclist labouring uphill.
An amphibious bird that easily walks on waterborne vegetation as well as climbing expertly into the branches of trees. The Moohen, unlike the Coot, rarely dives but picks its food (pondweed, duckweed, leaves of waterside plants, insects, worms etc) from the water surface as it swims. FAB.