Now, the U.S. Coast Guard is calling on anyone that saw the collision to come forward.
The Playpen is a place where boats anchor near Navy Pier and people aboard hang out. But Saturday on the water turned into tragedy.
"There were six to seven individuals on a floatation raft. While they were on that raft, another boat reversed into them, sucking them right underneath their boat," said Ark Pachnik of the CPD Marine Unit.
Two women, a 34-year-old from Chicago and a 28-year-old from Washington, were seriously hurt.
They were both taken to the hospital. One victim had both of her feet severed, while the other was missing her hand.
"The individual with her hand, it was severely severed I don’t know the extent of, I know I had to apply pressure on her wound. I had to apply pressure on the wound, I made sure she was safe from falling back off the boat, I applied the tourniquet to minimize the bleeding," said Raul Echevarria, CPD Marine Unit.
The U.S. Coast Guard says the collision happened between the La AquaVida and a 33-foot boat. The two women were on a float tied to the back of that boat.
Investigators want to hear from passengers aboard the La AquaVida at the time of the incident and are looking for video.
FOX 32 Chicago called the rental company for La AquaVida, and we were told they had no comment.