When taking beginners climbing it's difficult to get them to the top but even more difficult to get them down. People on the ground are always good at giving advice like "just stand up", "walk backwards", "sit in you harness". "But how can I stand walk and sit at the same time"? They reply.

On slippery wet rock as in the photo a good lowering position is particularly important. If your feet are too low then the normal force on your feet against the rock will provide a torque about the centre of mass (approximately where the rope is attached). This needs to be balanced by an opposite torque which is provided by friction. Friction is proportional to the normal force which gets less as the feet get lower. If the rock is slippery the friction isn't enough and the body will rotate until a clockwise force is provide by the nose hitting the rock.

The student in the photo has it about right. If the body is perpendicular to the rock then there is no anticlockise torque so no friction is needed to balance it.

Here is the usual animation made in Interactive physics.