We have often run night races on lakes when there are few fishermen out, just us catsailors in the lovely full moon. This is great fun, especially getting to weather marks almost by feel- how to not overstand or understand at night when depth perception is hard. Close crossings with other boats means judgement is honed carefully to be close but not too close! I got some broken and discarded strobe lights from highway hazard markers and repaired them to float on our homemade marks.
However Florida DNR "Enforcer" Jesse Crews busted me many years ago for sailing a Hobie16 after dark: I had to go to dang court to get it thrown out. This guy waited 3 HOURS for me to come back in to the ramp! Sometimes they don't know, or Ol' Jesse was breathing hard for 3 hours- "Oh Boy, I'm Gonna really Bust this one!"