The girls were playing in the water with a group of children when the younger sister was pushed down into the water.
Destiny Bahena tried to help but lost her own life in the process Saturday at Lakeview Beach in Beverly Shores, Indiana, which is part of the Indiana Dunes.
Bahena's six-year-old sister remains in stable condition at an Indiana hospital as family and friends try to help her recover from the ordeal and cope with the lost of her sister.
Parents like Abby Chambers at the beach Sunday remained shaken by the holiday weekend tragedy.
"She's not allowed in the water unless we're up here, and she don't go past her knees unless we're in there with her," said Chambers. "So we're just, we're careful."
Bahena died shortly after she was plucked from the lake, where she was found floating in waist-high water.
Children she was playing with tell authorities that she got into trouble while trying to save her 6-year old sister, who was being carried away from the shoreline by the waves.
Allen Pan and his wife briefly stopped at the beach Saturday afternoon with their three-year-old son, Ethan, after spending the day picking cherries in Michigan.
"We heard someone shouting from the waters saying, 'Hey, come here,' then we saw a man pulling out the girl, and the girl is pretty much unconscious," said Allen Pan.
After first responders administered CPR to both girls, they were transported to an area hospital where Destiny was pronounced dead.
The ordeal has frightened nine-year-old Eilish Chambers.
"If you get far and then the waves are tall... you could get carried away farther back," said Chambers.
Sunday afternoon, a safety patrol sailed along the shore where no lifeguards are on duty. Locals like Jim Sphect warn everyone to be careful.
"We're devastated," said Specht. "It was just terrible seeing that poor girl pulled out of the water."
A lot of locals in the Beverly Shores area said this is unfortunate but sometimes common occurrence during the summer.
There are signs posted warning beachgoers that there are no lifeguards on duty. Safety patrols are visible, but the public still has to be careful.