The 63-year-old was found unconscious in a massage pool at the Royal Plaza Hotel around 9:20 a.m. on Thursday, The Straits Times reported.
A lifeguard pulled him from the water and administered first aid before alerting the authorities.
He was then rushed to a nearby hospital for emergency treatment but was declared dead about an hour later, according to the South China Morning Post.
The man had been traveling in Hong Kong with his wife and was planning to stay until mid-October.
The exact cause of death will be determined following an autopsy.
His family informed police that he had a history of high blood pressure, according to a report by Sing Tao.
Singapore's Ministry of Foreign Affairs has confirmed that it is providing consular assistance to the family of the deceased.