I've never heard Jochen's side of the story, but had it recounted in great detail by Geoff in a talk he gave in Bristol.
In brief, and trying to be objective:
During the explorations that eventually connected Keld Head with the downstream sump in KMC, Geoff and Bear Statham were sometimes joined by Jochen Hasenmayer, an extremely experienced cave diver, up there with the best.
On one dive, 5th February 1978, according to Pitlamp, Jochen was slightly ahead of Geoff and had a route-finding problem when the line pulled away from the route that he had taken. This was exacerbated when he found himself almost alongside Geoff, but unable to reach him, as the passage between them was too low to pass. He was, however, able to pass his hand through and was, for a short time, holding onto Geoff's arm. Aware that Jochen was well off route and seemed to be unable to get back, Geoff's comment was "I thought I was shaking hands with a dead man." However, his worst fears were unfounded as, in due course, Jochen, having let go of Geoff as he realised that the route between them was not feasible, managed to find his way back through the beddings and thus out of the cave.
I also remember Bear saying that by the time that they did the through dive, they were so familiar with even that part of the route that they swam past without even a second thought.
Sad loss Bear. Lovely bloke. I remember sherparing for him on his first ever cave dive in Ireby Fell, a hook up with southern softy namby pamby divers & sherpas organised by one Oliver Lloyd.