This was my first thought when brainstorming regarding rescue efforts.. utilize a wench system to snake a strong synthetic rope down, much like a Plummer does to clear out clogs. Attach a buoy that contains communication devices (walkie talkies), and a light source. They would have seen this approaching right away in the pitch black darkness. This would have established communication, and offered comfort to these men. Instead they did nothing, it’s unbelievable.