We just came back from Cancun last night. We visited Xplor Cancun on March 16. The first thing we tried was the zipline (as everyone recommended from Tripadvisor). When we reached Tower 5 to Tower 6 , an accident happened. My son, a 19 year old weighing 135 pounds, stopped about 10-15 feet away from Tower 6 hanging in midair. The staff hooked on his gear and tried to reach my son, but a mom with a young girl had already been released down the same zipline from Tower 5. I saw them collide and the young girl started to scream. When the staff brought them back to tower6, the young girl was hurt very badly. The girl said that her tooth had been knocked out and I saw blood on the mother's forehead. My son was bumped on his shoulder and was left with a 1.5 cm diameter open wound. Before we entered the park we were asked to sign a consent form, but it only applies to unavoidable accidents. This incident was compltely caused by "HUMAN ERROR". The staff should not release the next person/group if the zipline is not clear yet, I don't know how much weight the zipline can hold, but with the lady and her young girl (about 6-7y/o ?) , my son and the staff all on the line at the same time, it could be overweighted. We don't know why my son stopped 10-15 feet before the tower. Maybe it is the zipline design, or the wind speed, who knows, but there is no precaution about weight or windy speed. My son ended up not being able to do the cave swimming and suffered from shoulder aches and stiff joint; I assumed the lady with the little girl left for emergency. After the accident, no one came to apologize or did anything. I noticed that some of the staffs were busy talking to their friends and was not even looking at the gear that he was hooking on. They did not ask you are you ready or not before they release you. We were extremely disappointed and concerned about the safety of Xplor Zipline.