Four children living in one family died instantly while swimming in Nakpangu stream in Yambio, Western Equatoria State.
The four deceased are school girls between 10 and 17 years old and ten-year-old school boy, Radio Anisa reported.
Two others on Thursday survived death narrowly in the same incident.
One of the survivors explains that his elder sister asked them to compete for an empty water container thrown into the water; unfortunately those in front of him started sinking into the water.
Family member Paul James says the six children went to wash their uniforms at the stream after school before started swimming only to meet death.
He added that two of the deceased are from the same parents and the rest are of in-laws.