Overgrown and abandoned

I came across this old structure along the banks of the River Nidd just outside Knaresborough. Nosey old me took a look inside and it houses old roofing tiles, rotten bits of wood and rope amongst other general detritus.
I'm not sure if it was meant to be a boat house at some time, as it is on the wrong side of the path, and about 25 metres or so from the river itself.
There's an old pipe running up the front and over the top, but I couldn't work out what that may have been for. (answers on a postcard please!)
It's being consumed by ivy and moss and looks rather atmospheric. It's certainly derelict.

After some deliberation I opted for the colour version here, but today's extra is the mono one which I nearly used instead.