A SUP is considered a "vessel" under the law, so it's important to understand what's required. You must follow the same "rules of the road" and safety regulations as other boats, but also practice defensive paddling to preventing collisions in spite of boaters who ignore "rules".
If you paddle at night, you need to show a white light, the same as a kayak or canoe. A flashlight or headlamp meets this requirement. A light with a flashing option is even more useful when you need help.
In the U.S.A. there was a 38% increase in participation from 2013 to 2014. SUP attracted the most participants in an outdoor activity. The median age for 2012 was 28 years old. (Outdoor Foundation: Outdoor Recreation Participation Topline Report).