Police said officers were called to the boat launch area off of Lakefront Promenade, near Lakeshore Road East, at around 3 a.m.
Const. Akhil Mooken told reporters at a press conference Thursday morning that due to the night time call, officers did not have enough light to definitively locate the vehicle. In the morning daylight hours, the marine unit arrived and divers went into the water, Mooken said.
Mooken said there was poor visibility under the water and the diver could only see about six inches in front of them. The diver was able to locate the sedan about eight to 10 feet deep in the water, but could not see inside the vehicle.
A tow company was called in and pulled the car out of the water.
In an update just before 1 p.m., Peel Police said a 25-year-old man was found deceased within the car.
A second occupant is believed to have somehow gotten out of the vehicle whether as the car was about to go in, going in or already in, Mooken said.
Later that afternoon, police confirmed the second occupant was a man. He was assessed at a local hospital.
Police said that he is cooperating with police.