The jolt, centred about five kilometres east of Christchurch, struck just after 5pm.
The earthquake was felt by thousands of people on GeoNet.
New Plymouth was rocked by three earthquakes in the space of five hours.
The quake hit at 9:30am, reported as having "strong" shaking, GeoNet says.
The group of divers are thrown side-to-side as the seabed begins to jolt.
Here's what we know.
There is no threat of a tsunami from the quake.
"Good thing we aren't in any danger, a wave would be well on the way here by now."