I know it's not scientific, but I googled "Cumberland River drownings" and got NINETEEN THOUSAND HITS. You know what happens to people who go into the Cumberland River? They don't come back out. The currents in that bad boy will bring even the strongest swimmer down.Some people did walk on the Cumberland in 1940, but not in June.
The only way to cross the Cumberland is if you can walk on it.
I did find one case where a Texas Confederate fighting alongside Nathan Bedford Forrest swam the Cumberland River at Donelson in February 1863 in driving sleet and set fire to Union transports. However, that 1 exception to Google's