Live crabs, stink bugs and ''miracle water'' are some of the most bizarre and potentially devastating things intercepted at New Zealand's border this summer.

Faced with record numbers of international visitors, Ministry for Primary Industries (MPI) biosecurity staff have been busy protecting the country's economy and environment.

Some of the more unusual interceptions include:

• A chilly bin of live spanner crabs from Thailand presented to officers at Wellington Airport.
• Fruit fly larvae in mangos found at Auckland Airport inside a suitcase from Malaysia jammed full of plant produce and other food.
• Freshwater fish from Thailand found crawling with maggots at Auckland Airport.
• Two brown marmorated stink bugs found during a search of a tent used by a traveller arriving at Auckland Airport from the United States.
• Untreated spring water from Fiji believed to have healing properties. Known as miracle water, travellers must pay for heat treatment if they want to bring the product into New Zealand.

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MPI screened 684,407 air passengers for biosecurity risk last month, an increase of more than 10 per cent (64,121) from January 2016.

It intercepted about 12,600 biosecurity risk items last month, including 1829 undeclared items.

"The interceptions show New Zealand's biosecurity system is holding up well in the face of huge numbers of arriving passengers, many of whom have little knowledge of biosecurity," said Craig Hughes, MPI's manager north passenger and mail.