Left bank (South) Island upstream of Frogmill Ait and downstream of Medmenham Abbey.
There is very shallow water around here and the navigation channel is towards the north right bank.
I do not know the derivation of the name. Culham Court was founded on Antiguan Sugar Estates which suggests slaves. Perhaps the estate owner brought a former slave to Culham and he settled here? The lane from here South to the A4130 Henley Road is 'Black Boy Lane' and the pub at the junction is Black Boys Inn.
I wonder whether the pub has history which can throw light on this?
Black Boys Inn
With origins, in part, dating back to the 16th Century the Inn is full of atmosphere and charm.
Oak beams, nooks, crannies and a wood burning stove welcome guests and act as a reminder of the Inn’s heritage,
while the modern facilities and contemporary country feel provide luxurious haven for our guests.
With seven guests rooms the Black Boys will delight any visitor dining or staying overnight while taking in the countryside views.
Just 5 minutes walk from one of the prettiest stretches of the river Thames.
Helen and Adrian Bannister kept the old name when they bought what had been a standard local boozer, but pretty much everything else has been transformed. The Black Boys is now an acclaimed gastropub with a classy modern British menu and excellent wine list.