It was his first time out on a new kayak in Bedok Reservoir - and it ended with him in severe pain and bleeding profusely.
Kian Wai Seetoh, 19, fell into the water after his kayak capsized near a pontoon several metres from shore.
As the Temasek Polytechnic (TP) student tried to climb onto the pontoon, he felt pain and realised something was biting the toes on his right foot.
The incident happened in September, as Mr Seetoh and his schoolmates were gearing up for the Polytechnic-Insitute of Technical Education competition.
Since then, there have been more cases of leg injuries, prompting national water agency PUB to suspend water activities from Dec 17 to Jan 16.
Recalling the incident, Mr Seetoh, a biotechnology student, told The New Paper (TNP) on Tuesday that soon after he fell into the water, he felt what seemed like the scales of a fish brushing against his leg. He then felt a fish biting his toes.
"The pain wasn't sharp. It was like the feeling you get when you get a...bruise, so I didn't expect it to bleed so much.
"When I got bitten, I pulled my leg out of the water. Then I saw the cut and the blood. It was gushing out. The whole pontoon was covered in blood," he said.
When he got out of the water and onto the pontoon, he was shocked to see gaping cuts around the toes on his right foot and blood spewing.
He then called for help. A teammate rowed out on a boat and took Mr Seetoh back to shore.
Soon after, his father arrived to drive him to Singapore General Hospital, where he received 13 stitches for his wounds.
It took three weeks before he could walk normally again.
Mr Seetoh was not the only victim of the mysterious attacks in Bedok Reservoir. Two of his teammates also sustained cuts after their boats capsized.
Since then, the TP canoe team has changed its training schedule, from six times a week to once a week. The school has also ruled that a teacher or coach must be present for them to train in the water.
Asked if he was now afraid to step into a kayak, Mr Seetoh said: "Not really, because once you get your balance right, the chances of you capsizing are very low.
"I started training again after four weeks."
In response to queries by TNP, a spokesman for PUB said: "Following the incidents, PUB had advised schools and water sports operators to remind their participants to exercise care when in the water, and to wear covered footwear and avoid submerging their feet in the water where possible.
"This is because some fish or turtles may bite when disturbed or when protecting their young. There has not been any incident since Dec 14 and we will continue to monitor the situation closely."
During the suspension of water activities at Bedok Reservoir, several fish - including a tarpon, African walking catfish, armoured sucker catfish and peacock bass - were caught.
An expert told The New Paper that none of these fish is indigenous to Singapore, and they had probably been released into the reservoir illegally.
Tan Heok Hui, a lecturer at the department of biological sciences at the National University of Singapore, said: "Introduction into urban reservoirs is usually via release by humans, either intentional or accidental.
Nature conservationist and advocate Ben Lee said: "For religious purposes, some people believe that releasing fish into water is a good deed, as the fish will be saved from human captivity.
"I have witnessed a group of more than 10 people, each with a bucket of hundreds of fish, wanting to release them into one of our reservoirs."
The introduction of new species could affect the ecology of the reservoir, he said.
"The catfish can be a menace to humans because it has poisonous spikes that can pierce and cause puncture cuts on the feet," Mr Lee added.
After viewing photographs of the wounds of Mr Ong and Mr Seetoh, Dr Tan said: "The small scrapes could also be from rough rock edges or small teeth plates that some catfish have.
"(As for) the larger gashes, (they) may indicate a wider cutting or biting edge, but the size is exaggerated by the human pull-away response. This could be caused by either fish or terrapins."
Those who illegally release animals or fish into reservoirs can be fined $50 for the first offence and $200 for the second. Subsequent offences will be prosecuted and offenders can be fined up to $3,000.
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