I am sure the "artists" are leaving their marks at night, because it will be too obvious in the daytime. After 9 pm (or an hour after the sun sets), I only see teenagers / youth hanging around the lake. Not being age-bias, I agree that security should patrol the lake more frequently at night, and security cam (or even warning signs) will enhance the effort.

The security guards used to chat for an extended time by the lake at night. Too bad they don't do it anymore.