"The Isis" is an alternative name for the River Thames, used from its source in the Cotswolds until it is joined by the Thame at Dorchester in Oxfordshire. It derives from the Latin (or pre-Roman Celtic) name for the Thames, Tamesis, which in the Middle Ages was falsely assumed to be a combination of "Thame" and "Isis". Notably the Isis flows through the city of Oxford.
The name "Isis" is especially used in the context of rowing at the University of Oxford. A number of rowing regattas are held on the Isis, including Eights Week, the most important Oxford University regatta, in the Trinity term (summer), Torpids in the Hilary term (early spring) and Christ Church Regatta for novices in the Michaelmas term (autumn). Because the width of the river is restricted at Oxford, rowing eights normally have a staggered start near Donnington Bridge and must then aim to "bump" the eight in front (i.e. catch up and touch or overlap with it sufficiently). The leading eight aims to "row over" (i.e. finish the race without being bumped).
There used to be ornate wooden barges on the river bank here at the southern end of Christ Church Meadow to house rowing facilities and for viewing races. Now the barges are gone and there are boathouses instead a little further down the river near the confluence with the River Cherwell. Poplar Walk in Christ Church Meadow is used as a route to and from the boathouses.