He was in the pool when he heard the lifeguard blowing the whistle, telling the swimmers to get out of the water.
Retiree Lee Song Joo, 59, then saw that a large number of dead bees had fallen into the pool.
He told The New Paper: "I did not see the bees when I was swimming, but I heard the lifeguard's whistle and he was shouting, 'Please come out, there are a lot of bees'."
It seemed like it was "raining bees", Mr Lee added, and many of them were floating on the water, with some dead bees on the ground.
Mr Lee estimated the number of people present to be about 80, including children who were screaming, turning the situation chaotic.
The incident happened at about 5.30pm at Yishun Swimming Complex, near Block 772 at Yishun Avenue 3, on Monday.
Mr Lee recalled: "They used nets to scoop the dead bees out of the pool and put them in plastic bags."
Chinese evening daily Lianhe Wanbao reported that the swimming complex was then closed for cleaning. About 10 workers were seen cleaning up with brooms and nets, and about eight plastic bags of dead bees were collected.
The swimming complex reopened at about 7pm.
Lianhe Wanbao reported that a big hive had been spotted at the playground at Block 771 on Monday.
Said Mr Lee: "I feel really lucky that I am not hurt, but since something like that happened, I will most probably wait for a few years before going back there for another swim."
This article was first published on July 24, 2014.
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