During WWII, the Japanese had themselves a plan to dominate the Pacific. To this end, they waged war in many places and scouted many more.

In early 1942, they made a stop in New Zealand waters at Mayor Island, in the Bay of Plenty. Some of the documentation says:

"...There is no evidence that the aircraft was seen or heard, but submarine sightingsa were reported about that time from the Bay of Plenty. The master of the fishing boat Waimana said that at 9.30 p.m. on 13 March, about 15 miles to the westward of Cape Runaway, he sighted a strange craft which looked to be very low in the water. When she arrived at Mayor Island next morning, the Waimana was boarded by a man who was quite positive that he had seen a submarine off the island. He described it as being painted dark grey and carrying a large gun. A third report was made by a fisherman working out of Tauranga that at 6.15 a.m. on 13 March he sighted a vessel, the description of which tallied closely with the Mayor Island sighting. It was considered probable that these sightings were of HMS Viti which was crossing the Bay of Plenty at the time on passage from Wellington to Auckland. When that ship arrived at Auckland, however, she reported having picked up a distinct hydrophone effect at 9.30 p.m. on 13 March, the indication being lost astern fifteen minutes later. A fishing vessel was sighted about that time."

A short time after the sub and aircraft sightings, some Tauranga locals visited Mayor Island and found the remains of a camp there along with 3 huge shells that had once been home to shellfish carried by the Japanese subs as a food source.

This is one of those 3 shells



It's Cassis cornuta, a shellfish that grows in the Pacific/Indian Ocean areas and this one now lives in the lounge upstairs. As you can see, it's looking a bit manky now which is to be expected from 60 odd years of knocking around, it has burn marks on the bottom where it was placed in the fire to cook; it carries the dirt of sheds and the bumps and bruises from growing kids (us), general daily life and moving house on quite a few occasions. As Cassis cornuta goes, this is not the biggest at 12 inches high and 11 inches across, they do grow up to 16inches.

Somewhere in the filing cabinet upstairs is some documentation about this visit by the Japanese and when I find it, I'll scan it and put it up here if it's any good. Until then you'll just have to do what we do; look at the big shell and think "that's a big feed of sushi".