Editing Drowning detection system (section)

=== Active systems ===
Active systems are often using a wearable on the swimmer, such as a wristband, that monitors the behaviour and position of the swimmer. If the swimmer is detected to be under water for a certain period, an alarm is triggered and through acoustic underwater communication from the wristband to receivers installed in the pool the alarm is transferred to on-site lifeguards that immediately can identify which pool and to start rescue. The advantage of such systems is that each person is guarded and that the same wristband can be used for access to facilities and lockers. The system is mainly used in public swimming pools where lifeguards are present.<ref>Sentag Pool Safety System https://www.sentag.com/ </ref>