As a cave diver (norwegian as well) i can tell you that a good light with a tight spot IS a incredible good way to communicate under water where there is no natural light at all. Lack of seeing your teams light is the first thing you notice. The only thing that could be better than a light is voice communication, but to do that in any meaning full way you will need to have a full face mask (like commercial divers) and that bring with them a lot of other problems. (like gas sharing etc). And Patrik did in-fact notice that Jari had a problem, and stayed 20minutes trying to help him before Jari died. The problem was the &quot;surprise restriction&quot; after point of no return.<p>So the problem wasn&#x27;t really a communication problem, but they didn&#x27;t follow good cave diving practice and thats most likely whats killed them. Normal cave dives starts and ends in the same opening, so you will never be at a point where you cant exit the same entrance as you started. When you do a more complex dive like a traverse as the Finnish did you always make sure you have dived ALL of the cave you want to traverse before! Normally you will do a setup dive from the other side of the system, and place a &quot;cookie&quot; (non directional marker) on the line where you turn. If you reach the cookie from the other side you can, if you up for it, continue to the other entrance. By doing so you ensure that everybody know of hazards like small and tight restrictions and that they dont catch you by surprise when you have passed the point of no return. (when you dont have gas&#x2F;scrubber time to exit the entrance you started from)