Lifeguards must maintain alertness and monitor an aquatic space across extended periods. However, lifeguard research has yet to investigate a lifeguard’s ability to maintain performance over time and whether this is influenced by years of certified experience or the detection difficulty of a drowning incident. The aim of this study was to examine whether lifeguard experience, drown duration, bather number, and time on task influences drowning detection performance. A total of 30 participants took part in nine 60-minute lifeguard specific tasks that included eleven drowning events occurring at five-minute intervals. Each task had manipulated conditions that acted as the independent variables, including bather number and drowning duration. The experienced group detected a greater number of drowning events per task, compared to novice and naïve groups. Findings further highlighted that time, bather number, and drowning duration has a substantial influence on lifeguard specific drowning detection performance. It is hoped that the outcome of the study will have applied application in highlighting the critical need for lifeguard organisations to be aware of a lifeguard’s capacity to sustain attention, and for researchers to explore methods for minimising any decrement in vigilance performance.