The one-year-old, who had just celebrated his birthday in November, was found unconscious in the pail by his mother.
The accident happened at Sungai Rambai, Jasin, Melaka.
Jasin OCPD, Deputy Supt Arshad Abu, identified the victim as Muhammad Arash Zahrain Osman.
"He was immediately rushed to a health clinic in Sungai Rambai.
"Doctors failed to resuscitate him after almost 30 minutes attempting to save him," he said.
DSP Arshad said the toddler's parents were having lunch when he wandered into the bathroom.
He said the toddler's mother thought that the pail was empty.
"It was only after she heard the sound of running water in the bathroom that she discovered the toddler's head down in a pail filled with water."
DSP Arshad said no signs of external injuries were found on the victim.
The victim's body will be sent to the Muar hospital on Dec 14 for a post mortem.