Lone Black Swedish Duck on River Medway

Hi there! I hope this is the correct place to post as I'm new to the forum. I'm currently on holiday in a cottage near the River Medway and we noticed a black duck with a white bib travelling up and down the section of river in front of us for the last few days and vocalising day and night (sounds distressed but might be natural behaviour!). I believe it's a Black Swedish Duck and that it's a lone female (quacking rather than rasping). I know this breed is domestic so it's probably an escapee but not sure if it needs help. Anyone know how these ducks fare in the wild?