Kaikōura Mayor said the water was dead calm at the time of the accident and the assumption was that a whale had surfaced from beneath the boat.
Norwegian whalers have hunted at least 570 minke whales in 2021 despite growing calls to end it.
Images of 10 orcas and 87 beluga whales, kept in enclosures in a bay near Sea of Japan port of Nakhodka, sparked international condemnation forcing the Kremlin to intervene.
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