Perhaps I'm not reading as much into what was asked of the poster to accomplish . . .
"He asked me if I would dive down and attach a cable or rope to the bumper so they could pull it out."
The only task requested of the poster was that he attach a cable or rope to the Jeep, that is all.
The only elements of this dive different from any other dive is reduced visibility and temperature.
The poster and his buddy called the dive because of the progressively worsening conditions. (However the separation of the buddies when one diver continued to a greater depth is not to be applauded)
The divers recognized the complications of the dive and have set about to plan a dive in such a way that it will be safe to accomplish the requested task.
Overall, I think they have shown, for the most part, good judgement and proper problem solving skills.
Diving with a diver "experienced" in this case will do nothing to change the temperature of the water, increase the visibility, reduce the increased SAC's due to a hostile dive environment and identify possible hazards in that given dive site. Those things are constants and are recognized as such by the participating divers.
the K