New Zealand is still celebrating after successfully launching its first home-grown rocket into space, however its builders are now desperately trying to find it.

The six-metre-long rocket blasted off from Great Mercury Island, an idyllic spot not far from Auckland, where U2 singer Bono once holidayed.

The noise sent sheep running. The rocket went 150 kilometres, entered space, then turned back to Earth and plummeted into the Pacific Ocean.

This morning, a fisherman spotted part of the rocket bobbing in the water.

One of the rocket's creators, Mark Rocket, who changed his name by deed poll, is keen to find the rest.

"It's got delicate instrumentation and we just want to know what the GPS coordinates are and we will go and pick it up," Mr Rocket said.

He says his team is planning to build another, much bigger rocket.