Connaught Water is a magnet for very rare, non-escaped, totally and utterly wild ducks. The number of waterfowl rarities hosted over the years beggars belief. In fact I am surprised that the wild Falcated Duck in Kent and equally wild Ferruginous Duck at Staines didn't end up there.
Despite their obvious wariness, with a stealthy approach you can often get quite close to them. A good technique is to just walk straight up to them when they are facing the other way, or are being distracted by bread, and then snap away hoping against hope that they don't notice you and fly away if they are able to.
Here is a selection of the latest nearctic vagrants, plus the undomesticated Red-crested Poch that arrived in a freak typhoon a few years back, and has yet to find the way home - probably lost its A-Z.