I&#x27;m not a diver so what I&#x27;m about to say may sound incredibly naive but I&#x27;m surprised they don&#x27;t use more advanced communication tech when diving than just relying on light signal.<p>They could use some kind of haptic feedback system working to communicate between each other through RF waves. If one person presses a button, the other members feel a vibration or some similar haptic feedback. This would allow people to signal danger more easily. It would also make sense to have a notification signaling when any member is outside of the RF range.<p>Having such a tech would have allowed Gronqvist to have directly been alerted when Huotarinen became stuck either by Huotarinen alerting him or by the notification that Huotarinen was outside of the RF range (which would probably not carry very far in that situation). If other members had been alerted faster, Huotarinen would have had less time to start panicking and would maybe not have needed that cylinder of gaz.<p>So, maybe I&#x27;m incredibly naive and there&#x27;s a good reason but it seems stupid and dangerous to rely on a torch to signal distress (which is often not going to be visible to members in front of the group).