The teen was taking part in a scuba diving lesson when she went into distress while underwater off Whytecliff Park, at around 4:45 p.m. PT Saturday.
Other divers brought her up and back to shore. She was unconscious but breathing and was airlifted from the park to Vancouver General Hospital, where she was listed as in critical condition in the intensive care unit.
Just under 24 hours later, at 4:15 p.m. Sunday, the West Vancouver Police Department said the girl's condition had improved.
Though still in serious condition and breathing with the aid of a ventilator, the girl was awake and had been speaking with her family, police said.
The West Vancouver Police Department said the instructor who was supervising the lesson is a qualified divemaster, and the incident is under investigation.
Martin Ernst, an assistant fire chief in West Vancouver, said there have been diving accidents at Whytecliff before.
"Every year we see three of four incidents out at the park. It's a very popular place to go diving," he said. "Diving is one of those sports. Things can go very well, when they go well, and they can go very wrong, when they go wrong."
Ernst said diving is a rewarding experience, but there are a number of things divers should do before heading to the depths, including making sure divers have the skill level needed to dive in B.C. waters, making sure equipment is in great shape, and always diving with a buddy.