The Rescue Co-ordination Centre in Victoria says the Cessna 172 had taken off shortly before the crash from the nearby Pitt Meadows airport. Initial indications are the float plane was on a training run at the time of the crash.
Captain Eric Niemi said the injured person was picked up by a pleasure boat that was on the lake at the time.
A rescue helicopter that was training in Squamish at the time then arrived and dropped a search and rescue technican into the water, who swam to the plane and pulled one body out.
It's unclear what caused the aircraft to go down, but Niemi said despite a light rain, flying conditions were good at the time. The Transportation Safety Board is expected to investigate the crash on Tuesday.