This is a canal lock on the Lea River near the Olympic Park. A canal lock lifts or lowers a boat from one water level to another. On this lock - the boats drop about 10 feet.
This is a camp ground of sorts. People could leave their boats at this little harbor - catch the Tube and go anywhere in the city.
In the USA - motor homes and trailers are very popular forms of recreational vehicles. Since England is still criss crossed by canals from the old days - many folks buy these old long and skinny freight boats and turn them into little campers or "floater" homes. They are about 8 feet wide - stick out of the water maybe 4 feet. They can by 70 or 80 feet long. They look like they only travel about 5 miles per hour. It looks like quite a task to prevent them from hitting the sides of the canals. Some of them look very expensive - others look like floating dumps. But on the canals - it looks like no one has precedent over the other.