Officer Tosha Ramirez told ABC13 that a call came in just after midnight Tuesday, reporting that someone had heard the crash.
There was only one person in the car, the officer said, adding that it had completely submerged into the canal.
Ramirez said the Galveston County Sheriff's Office Dive Team responded and was handling the investigation.
"Their dive team came out, and they did an amazing job," Ramirez said. "Once we confirmed that it was going to be an accident where a vehicle was in, had gone into the water, that's when the Galveston County was called out, and they ended up taking over from there."
The victim has not been identified, according to police.
The officer said they are also still determining which way the person was driving and what caused the accident.