American Victor Huang, 31, from San Fransisco, was diving near the Wahine Memorial off Wellington, New Zealand.
He was filming the sizeable octopus with his brand new Panasonic Lumix digital camera, coloured a bright blue.
The octopus, lying in kelp on the seabed, suddenly put out a tentacle, taking hold of Huang's wrist as other tentacles closed around the shiny camera.
It was prised from his hands and the octopus shot off. The diver went after it and managed to catch up after a chase lasting for several minutes.
Cleverly he distracted the octopus by holding out his speargun, on to which the creature promptly clasped.
This loosened its grip on the camera, which by now was at its mouth. After "a bit of a wrestle", Huang was able to grab it back.
Unperturbed, the octopus remained attached to Huang’s speargun, intent on more fun.
It accompanied the diver for a while as he finned about, until it finally tired of the ride, relaxed its grip and left.
Huang’s resulting video footage, which captures the snatch, the camera's tentacle-cosseted ride and the speargun antics, can be seen at www.youtube.com/watch?v=x5DyBkYKqnM