The guilt is the worst.
Carolyn Smith sits on the porch of her mother's Coal Creek home looking out at the rain, thumbing away tears.
"People don't give that enough credit, but survivor's guilt is a terrible thing."
Smith was 18 when she stepped onto the platform at Cave Creek with her classmates and a Department of Conservation (DOC) ranger. The students were from the Tai Poutini Polytechnic's outdoor recreation course and were at the site near Punakaiki for a lesson in geology.
They stood on the platform to look below at the Cave Creek resurgence, where the stream emerges from an underground cave system before heading out to sea.
It was a bright, sunny morning on the West Coast when the poorly built platform collapsed, sending 18 people plunging 30 metres into the canyon below.
Smith was one of four survivors and for 20 years she has wondered: Why me?