Hertford Union Canal
The Act authorising the Hertford Union was passed in 1824, and it opened without a great deal of ceremony in the spring of 1830.
The canal linked - and still does - the Regent's Canal to the Lee Navigation, avoiding the distance via Limehouse and the semi-tidal Limehouse Cut. It runs alongside Victoria Park for much of its short length of just over a mile, with three locks. The canal is also known as Ducket's Canal after Sir George Duckett, its original promoter. It was never a great commercial success and indeed for a time from the late 1840's to the mid 1850's it was unnavigable. In 1851 it was advertised for sale but no buyer wanted to invest in it. Eventually the Regent's Canal bought it and from 28th October 1857 onwards it became a branch of the Regent's Canal and from 1929, part of the Grand Union system.
The canal provides a pleasant cycling route into London from East London and although you're no longer required to dismount under the narrow bridges that adjoin the three locks, I'd advise it as an alternative to an unplanned swim.