The three friends, who had gone to Bandra Bandstand on Monday morning, had lied to their families and left home saying they were going to college.
The families later received calls informing them about the incident.
"We had no idea he had bunked his lectures and come to Bandstand with his friends," said Shabina Sheikh, sister of 18-year-old Irfan Sheikh, who drowned.
"We thought he was in college until we received the phone call informing us that he had drowned."
Sheikh lived at Naupada, Kurla, while his friends Masleuddin Hashmi, who also drowned, and Hody Jaiswal lived in Dharavi.
Sheikh lived with his mother, sister and brother. His father passed away a few years ago. Shabina, who works in a private firm, and his older brother, who works in Mangalore, support the family.
A police officer said the three boys were very good friends. Jaiswal told the police that they would often go out together. "Sheikh and Hashmi met in the morning and went to Jaiswal’s house. After he came, they said that they had decided to go to Bandstand," a police officer said.
The trio went to Bandra from where they first purchased two pints of beer. Sheikh and Hashmi drank it while Jaiswal refused. They then went to Bandstand and decided to go for a swim.
Jaiswal only took a dip in the water and decided to return to the shore and watch because he did not know how to swim.
A distraught Shaukat Hashmi, Masleuddin’s father, who works in a zari workshop, refused to speak. "He is gone. There is nothing I can say or do now to change what has already happened," he said.
Police Sub-Inspector K.J. Gadve, said, "Whether the duo had consumed alcohol or not will be ascertained only when the post-mortem report is out."