SINGAPORE - The double deaths were not just rare, they should not have happened at all.
Mr Song Shing Hae, president of the Singapore Underwater Federation, the national sports authority for diving and underwater activities, said this emphatically.
"Unforeseeable circumstances can catch even the most experienced instructors by surprise. But it is important to mitigate all possible incidents."
Although investigations are still underway, dive experts give The New Paper some possible scenarios.
1 Lack of air
The Tioman dive shop operator, Mr Reynolds Esteva, claimed that checks after the accident revealed that Dr Lee Yong Yeow's tank, had run out of air while instructor Tan Seah Heng had 30 bars of air left, reported Shin Min Daily News on Monday.
Divers would usually start their dive with 200 bars of air and resurface when there is 50 bars of air left.
Instructors would also not risk allowing a student to dive without a full tank during training, said Mr Song, who has more than 30 years of diving and instructing experience.
In a situation where a diver runs out of air, another will share air with their buddy via an extra hose, also known as the octopus. Divers are also supposed to check the amount of air that is left in their tank every 5 to 10 minutes, said the experts.