The jobs of more than 100,000 New Zealanders are linked to the seas which circle the country.
The output from those workers, the ports, fishing fleets, marine farms which employ them, and revenue from offshore oil and gas resources adds 1.9 per cent or some $4 billion to New Zealand's GDP each year.
The marine environment then is a significant component in the national economy. Whether it remains so, however, is uncertain because it faces stresses and threats from a number of directions.
A new report from the Ministry for the Environment and Statistics NZ titled Our Marine Environment 2016 attempts to assess the scale of these challenges so that policymakers might have unambiguous conclusions to make informed judgments.
The report comes up short, simply because the state of existing knowledge is limited.
There are some things we do know about the marine environment.
Greenhouse gas emissions are making the oceans warmer and more acidic. This global physical change has a momentum which this country, by itself, is powerless to stop, though the report notes that New Zealand's net emissions per person are among the highest in the world.
Warmer oceans mean rising sea-levels, which has worrying implications for the thousands who live by the coast. The scale of potential harm is a concern because more acidic seas threaten the survival of marine species which in turn could damage fish farming, traditional Maori seafood gathering and commercial fishing.
The outlook for marine diversity is likewise hardly comforting. The full picture is again limited but where the science is sound the news is not good. More than one third of native seabird species, half of our shorebird species and over a quarter of signature marine creatures - penguins, whales, dolphins and albatrosses - are threatened with extinction for a host of reasons.
Some pressures which imperil these animals - pollution, loss of habitat, fisheries bycatch - can be checked, but what is clear is that extinction of any species could have a knock-on impact on the broader marine ecosystem, and dent New Zealand's reputation as a guardian of marine fauna.
Coastal marine habitats are not, the report confirms, in the best shape. These are our treasured summer playgrounds, and are under pressure from sediments, damaging fishing methods, marine pests and nutrient loads from farming and urban runoff.
Change in these areas - such as the Hauraki Gulf - happens over decades. Degradation in their health causes longterm and costly harm.
Fishing is the other big issue addressed in the report. Up to a point, that is. The authors admit that due to a lack of data it is impossible to draw any firm conclusions about the impact of commercial, recreational and customary fishing on marine ecosystems.
This is a shortcoming because 17 per cent of commercial stocks were overfished last year, and rebuilding requires intervention.
In all these areas - climate change pressures, threats to species, destruction of coastal habitats and overfishing - gaps in the state of current knowledge means much remains unknown about our marine environment.
New Zealand is a maritime nation and its future rests on healthy and resilient seas. It is imperative that the state of knowledge is improved so we can better deal with the testing times ahead.