New Zealand police have named the English tourist who died in the Kawarau River on Tuesday after becoming trapped between rocks while riverboarding.

She was Emily Louise Jordan, 21, of Worcester in central England.

Ms Jordan was travelling with her boyfriend who could only look on helplessly as rescuers tried to save her after she was pinned between submerged rocks in rapids.

The group were riverboarding with the adventure tourism company Mad Dog Riverboarding from Queenstown in southern region of the south island.

Police said river guides taking the group struggled for about 20 minutes to free Ms Jordan and return her to shore to begin CPR.

Emergency Services were called but they were unable to revive Ms Jordan.