He's passionate about birds and frequently goes to Sungei Buloh Wetland Reserve to observe them.
But one thing caught Mr Ben Lee's eye last Sunday and there was nothing natural about it.
He saw three people paddling on a raft, made of what appeared to be a large piece of styrofoam, and cast a net into the water.
According to NParks, the number of people caught fishing illegally at parks and nature reserves has almost tripled in the past three years.
At around 2.30pm on Sunday, Mr Lee, 52, the founder of nature conservation and environmental group Nature Trekker, was at the nature reserve with two other volunteers from the group when he spotted the three people - two men and a woman - in the distance.
He used his camera to zoom in on them and saw that they had a paddle and a drift net.
He took several pictures of them before calling the police and telling the nature reserve employees about it.
He said: "They (the illegal fishermen) were too blatant. Sungei Buloh is a place where nature is supposed to be protected, and yet poaching takes place."
He added that the poachers were about 1km away from the viewing platform, so visitors could have thought they were the reserve's employees.
Mr Lee said the three people put the net into the water and left. They returned half an hour later.
This time, the woman was not with them but a third man had joined in to inspect their catch. They lifted the net and put the fish they had caught into a small styrofoam box.
He said: "When they pulled out the net and placed it on their raft, it was very big. You can only imagine the amount of fish they caught."
When contacted, NParks told The New Paper that their officers were alerted to the incident and went to investigate.
Ms Sharon Chan, Sungei Buloh Wetland Reserve's deputy director, said the fishermen were questioned at the scene with the assistance of the police.
She said: "The net used was also confiscated.
"As investigations are currently ongoing, we are unable to provide further information on the incident."
Dr Hsu Chia Chi, chairman of the Marine Conservation Group in Nature Society (Singapore), said fishing alters the balance of an ecosystem.
He said: "Abandoned equipment may also act as long-term killers of both underwater and inter-tidal fauna."
Fishing nets left behind could trap and kill fish, and small mammals like otters.
Fishing hooks left impaled in fishes could kill animals higher in the food chain that consume them, he added.
Mr Shawn Xue, an avid angler who runs the Singapore Fishing blog and Facebook page, didn't mince his words.
He said: "I feel the actions of these particular fishermen are deplorable, specifically because they are fishing in a nature reserve, a place where nature should be able to flourish, mostly undisturbed by human intervention."
Sungei Buloh is a place where nature is supposed to be protected, and yet poaching takes place. - Mr Ben Lee
This article was first published on Jan 14, 2015.
Get The New Paper for more stories.