They're almost as rare as hen's teeth, but Jim Eagles finally lands his shark tooth in the Chathams.

Aha, at last, just what I was looking for, a glint of blue-green shining out of the white sand. I bent down, and, sure enough, it was a fossilised shark's tooth, about 30 million years old.

I'd read that these incredibly ancient objects could be found in the Chatham Islands, mostly around the shores of the great Te Whanga Lagoon, but our first effort to find some was a failure.

We spent hours scouring the shore around the lagoon entrance, near the traditional Moriori meeting place at Te Awapatiki, without finding a single tooth.

I was so disappointed, and so desperate to have one of these extraordinary mementoes, that I negotiated a deal to buy one from 6-year-old Sasha Galvides, a local collector.

The previous day, Sasha had shown me his collection; a jar full of teeth, some of them scarily large.

Our island guide, Val Croon, had told me, "Sasha is amazing. He just walks along and they almost jump up into his hand," so I figured he might be able to spare one in exchange for a bit of pocket money.

He was - though only after some tough bargaining - and by the end of the day I was the proud owner of a rare Chatham Islands souvenir.

But now at Blind Jim's, I was actually able to find fossil teeth myself ... albeit much smaller.

It took only a minute for one of our group to spot a big tooth complete with its root, about 4cm long, probably from Eugomphodus macrotus which swam these waters 37 to 55 million years ago.

Soon after I saw a smaller tooth.

The presence of these teeth has been known for hundreds of years. They were apparently highly prized by the Moriori who settled the Chathams some 500 years ago and used as gifts on important occasions.

To find a tooth from a creature that was eating fish long before the first primate - let alone the first human - walked the earth was amazing.

When I think about it, the very idea of this little tooth being 30 million years old was hard to comprehend.

I kept looking and soon spotted a few more. I ended up finding 11.

What I didn't find, but Sasha has in his collection, was a tooth from a modern shark, large, white and scarily sharp - a reminder that even today the rich waters around the Chathams stock more than just delicious crayfish.

As we drove round the island, Val pointed at beautiful beaches or spectacular rocky outcrops and told stories of the fearsome sharks found there.

The most amazing tale was about paua diver Vaughan Hill who lost an arm to a great white some five years ago and nearly died. He still goes diving today.

A former paua diver himself, these days Val runs the Hotel Chatham and operates Great White Shark Dive NZ, which offers the chance to dive with great whites inside the protection of a cage. "We've got some guys coming up to go cage diving next week," he said.

Further information: Pukekohe Travel run all-inclusive tours to the Chatham Islands. Ring 0800 785 386.

Jim Eagles was taken to the Chatham Islands by Pukekohe Travel.