Something that Edd said during the "Disappeared" episode- said it was possible for someone to go farther than he did if they had no intention of coming back. Said they could have to take their tanks off and go through some tiny cracks. It was sort of conflicting- in one instance he stated that Ben is not in the cave. In another he said that he could be had he intended to commit suicide (ie, slip through a crack that he could not return from). Based on the evidence presented, I think this is the only logical conclusion. His car, money, and some diving gear was left at the dive site. People saw him enter the cave. He has never been seen since. Logically I have to conclude he verntured into an area that he had no intention of ever returning from. ** Note- not a diver, just someone really intrigued by the story after watching it on TV.