Coastal surface waters in the South Atlantic Bight contain elevated activities of 223Ra(t1/2=11.4 days) and 224Ra(t1/2=3.66 days). These elevated dissolved activities are due to continual input of the short-lived tracers near the coast. The presence of these tracers in an offshore water sample implies that the water is less than six half-lives removed from the source of the tracer. The absence of the tracer implies the water is more than six half-lives old or has been diluted substantially with old water containing little tracer. In this paper I use models based on 223Ra and 224Ra to derive ages of continental shelf waters. These models compensate for tracer dilution by normalizing the short-lived tracers to each other or to long-lived 228Ra. If the water on the inner shelf (0--20 km from shore) is assigned a zero age, ages for waters 80--100 km from the inner shelf are 20--30 days. ¿ 2000 American Geophysical Union