system
Given the following post, respond as if you're commenting on Reddit:
human
If dimples on a golf ball increase distance, and denticles on a sharks skin decrease hydrodynamic resistance, why are barnacles bad for ships, aside from weight?
gpt
The dimples on a golf ball create turbulence which normally increases drag, but in the particular circumstance of the golf ball, it actually reduces drag. The reasoning is totally not intuitive and easy to explain, but it has to do with the turbulence allowing the air flowing around the ball to detach (stop being laminar flow) early which creates a barrier that allows air outside the turbulent layer to flow more optimally, in the shape of a boattail. This in turn reduces the drag. 

This trick of adding additional turbulence to reduce drag only works in very specific circumstances and conditions. You can't add vortex generators to any circumstance and expect it to work better than without.