The photo can't be 1903 because the wind mill was demolished in 1878 after being there since 1777.
I, too, was wondering how the boat got near the mill.
Here's another fair-sized boat just below the dam.
The railway embankment for the line to Price's Candle Works, etc., was built in 1910 but before that the River Dibben would have had a clear run down to the Mersey, apart from the Dam, which provided the head of water for the mill.
The high view with the car (bull-nosed Morris?) would have been from the railway level.
The early maps show that the river was tidal, way up into Brotherton Park, presumably at extreme high tides. The mill race bypassed the dam but I assume the boat could have got up that way, so it may have over-topped the Dam at one of the high tides, assuming the railings weren't there.
The other boat is in what would have been the normally tidal part, before Bromborough Dock was completed in 1930.
I lived at the other end of Bromborough Road, Lower Bebington, up to the 1960s and well remember the awful smell and the yellow oily water below the Dam. They dumped chemicals from the factory further down stream apparently but the river flow was not sufficient to keep the water 'sweet'!
Try to imagine the rural scene before any of the industry got there. Lever chose the Dibben inlet from the Mersey to have water access for the import of the soap ingredients and packaging and the export of his products to the rest of the world. The River Dibben was never the same again! Most of it below the Dam seems to be hidden in pipes now?
Bri
Description: Windmill was demolished in 1878
Description: Another boat, below the dam
Description: The culvert being built, 1910
Description: A test train?
Description: Before the railway embankment (Tidal in blue)
Description: The dam and the mill race
Description: In Brotherton Park, tidal limit