You don't HAVE to take a class to dive at night, but diving at night IS different. If you are going to try it on your own, I'd recommend starting at dusk, in a site where you feel very comfortable and know the navigation pretty well, and if possible with a buddy who has done it before.
Site topography looks different at night, and buoyancy control in midwater in the dark is more difficult, since you don't have the gradation of light to orient you.
Site topography looks different at night, and buoyancy control in midwater in the dark is more difficult, since you don't have the gradation of light to orient you.