To prevent drowning incidents in French public swimming pools (PSP), bathing must be constantly supervised by qualified lifeguards. However, fatal drownings regularly occurs in supervised aquatic facilities, calling into question the efficacy of the supervision chain. The aim of this research is to fully assess the periods during which supervision is not carried out, or carried out in an inadequate manner. The observations made in 108 French PSP show that constant supervision, as stipulated by regulations, represents only half of the time. Over a total observation time of 54 hours, 147 periods during which the supervision system was degraded for 3 min or more were noticed. In the worst-case scenario, this possesses a significant problem in terms of survival probability without sequelae.