A seven-year-old boy drowned at the Hard Rock Hotel at Resorts World Sentosa in June after venturing into a section of the swimming pool deeper than his height.

Muhammad Syafizul Danyal Muhammad Shaffie, who was 1.15m tall, strayed into an area which was also in a blind spot to lifeguards.

It was the second such death at the hotel. In February 2012, a six-year-old girl from Hong Kong, who was 1.14m tall, drowned in the same pool.

Yesterday, State Coroner Marvin Bay found Syafizul's death to be a "sad misadventure", saying he "would likely have had trouble staying afloat in the 1.2m-deep zone".

The coroner said parents and providers of swimming and water play facilities must be vigilant when children are in the water. "Young children are prone to act in an unpredictable manner," he said.

The coroner's court heard that on June 14, Syafizul and his brothers, aged eight and nine, went to the hotel with their grandmother. She took him to the pool at about 4.40pm and asked an 11-year-old family friend to supervise him.

She told Syafizul to play only in the 0.85m area before she went to the sun deck area.

At about 6pm, two hotel guests, aged 13 and 23, were playing at the 1.2m area of the pool when they saw Syafizul motionless and facing downwards. They thought he was playing in the water as they saw bubbles coming from his mouth.

Five minutes later, when they saw he was still motionless, one of them dipped her face in the pool.

She saw that his eyes were closed, and he did not respond when she tapped his head. The two guests shouted for help and tried to pull him out.

Two lifeguards performed cardio-pulmonary resuscitation. Ambulance paramedics arrived at about 6.10pm; Syafizul could not be revived and died at Singapore General Hospital at about 8.30pm.

The court heard that before Syafizul's drowning, the hotel took steps, such as setting up barriers indicating changes in depth and hiring lifeguards, to improve safety.

There are no CCTV cameras in the area as the hotel felt it would make guests uncomfortable. The hotel has since hired a third lifeguard.