Several men are sitting by a river conversing with one another while a boat drifts by them .
It is probably the case that several men are sitting by a river , about to go swiming .
It is improbable that several men are sitting by a river , about to go swiming .
It is probably the case that several men are sitting by a river , about to go swiming .
Several men are sitting by a river , about to go swiming .