Ayanna Patterson was apparently dragged underwater by rip currents.
Saturday, a rip current advisory remained in effect at the beach.
Parents have been keeping their children close to shore.
"We get in maybe briefly to cool off but we hold onto them and keep them in the sand," said Kim Watschik.
"We're here with our children and are totally tuned in to the fact that we have to be very close at all times," Andy Kaplan said.
"Everyone needs to keep an eye out for each other, swim in groups, stay near the lifeguard and let the lifeguards know if they need assistance," said aquatics manager for the Chicago Parks District Eric Fischer.
Fischer also says beach-goers need to be aware of the flag system.
A green flag means swimming is permitted, yellow means caution is advised and red means swimming is prohibited.