A student who survived a Taranaki rock-climbing tragedy has described the intense panic that set in when he thought he would not get out alive.

Spotswood College student Campbell Shaw and two other students fell into the water during an outdoor pursuits exercise at New Plymouth's Paritutu Rock on Wednesday. Campbell was rescued and instructor Bryce Jourdain dived in to try to save the others.

The three are still missing and police said the official search for the bodies was being scaled down on Saturday.

Campbell told TVNZ's Close Up programme on Friday there were no words to describe the ordeal.

"It was just pure panic. I didn't think I was going to survive myself."

He said the conditions initially had been perfect.

"We weren't supposed to be going to the rock. We were meant to be doing something else, but the decision was made and it was a fine day. But as soon as we got there, the clouds came over and it was raining."

He said everyone was excited.

"It's just a bit of harmless fun, we're all fine, we've got harnesses, it's all good. But it's just a certain point we got to, the waves became too big."

The harnesses reportedly were not attached to anything when the waves hit but the students were standing on a flat area of rock where they should have been safe.

Campbell also talked of Jourdain's bravery after hearing that Stephen Kahukaka-Gedye and Brazilian student Joao Felipe Martins De Melo, both aged 17, had been swept away.

"As soon as he heard that the students were in the water, he just instantly dove in."

The centre's board chairman, David Grigg, said it had started an internal investigation into the tragedy.