Macao police are investigating the death of a Chinese mainland businessman who drowned to death in a massage tub at the Four Seasons hotel on April 4, according to local media reports.

The victim, 37-year-old Wu Jinsheng, was reportedly in the massage tub, when a malfunction occurred to the tub's pump, which intensified the backwater flow at the bottom of the tub.

Wu was sucked down to the bottom of the pool, submerging his head.

The tub is 3 metres long in diameter and 0.9 metres long in depth.

Wu's wife and other vacationers attempted to pull the businessman out of the tub, but the force of the pump's suction kept the business submerged. It wasn't until 20 minutes later did the staff at the hotel turn off the power to the pumping system, but Wu had already drowned to death.

Wu, along with his wife and child, checked in to the hotel on March 31 during a holiday trip.

Wu was the biggest shareholder of a Shenzhen-based technology company that develops bio-metric security and timekeeping systems.