sail up the/a/(some) river
To travel in a boat, especially a sailboat, upstream through a river. I managed to sail up the river by constantly adjusting my position in relation to the current and the wind. The navy vessels sailed up the River Thames as part of the Remembrance Day festivities.
sail up a river
to travel upstream on a river in a boat or ship. We sailed up the Amazon River in a large, seagoing ship. It was not possible to sail up the Mississippi as far as we wanted.