Abstract: A portable bather monitoring device, for example in the form of a wristband device, incorporates a pre-alarm to emit a warning signal to a bather to forewarn him that he is operating outside a defined rule-set in such a way than an alarm will be generated in a predetermined time unless he modifies his behavior or actively operates a delay to the alarm. The pre-alarm is notified to the bather by audible, vibration or other means and an override input is provided which in defined circumstances allows the bather to delay generation of the alarm used to alert waterside staff to the fact that a bather is in danger and requires immediate assistance.