Not gonna dwell on the recent drowning incident that happened during the Dragon Boat Race. Just gonna let you, the reader know why you shouldn't swim in this dam.
Well, first reason is common sense. This is after all a catchment area that provides water to the surrounding areas.
Secondly, ( what some people suspect) there are underground streams flowing into this place from the hills.
So while the water looks still, you can't tell if there is some sort of current that can pull you under, especially when it's been pouring uphill.
Next reason is this ( what I heard from some older folks)