Some of them are caught in weird 'shapes' but several of them are pretty clearly ducks, so I think they all must be. They all look the same size and coloration.
There's just a hint of grey on the wings of at least one bird in the bottom shot - I think they may well be Garganey.
Ducks quite commonly fly quite low over the surface of the sea like this when migrating, though they also fly quite high over the sea at times too.