You can hire a faluka to take you down the Nile for however long you want...
take food and water, wine and/or beer, whatever. We used to do this with the kids -- a great picnic opportunity, and no sand or flies (unless the wind stopped) and if the wind stopped, which it would do, we would be marooned out in the Nile until it came up again. So, if you take a faluka trip, don't plan anything too close to your return time.