IIRC,It's been a long time since I did any marine enforcement,but,I sure remember that leaving anything out in the water after dusk and before sunrise,unmarked,can be deemed an "obstruction to navigation" with severe penalties should there be a collision much the same as cottagers leaving floating rafts out overnight. Everything left out overnight must have it's own navigation light system visible at all times. Smart people tow them in when they're done using them.