Up to 10,000 containers a year are lost from ships worldwide and the Insurance Council says they are "floating disasters waiting to happen".
Chief executive Christopher Ryan has issued a warning - to everyone from America's Cup yachtsmen to recreational boaties - that rogue containers bobbing at seathreaten lives.
The council today launches an awareness campaign in Wellington to try to get support from maritime groups, the Government and the public to put preventive measures in place and ensure lost containers are safely recovered.
"The increasing numbers of passenger ferries throughout New Zealand, and the increased use of recreational boating is now at such a level that the insurance council feels compelled to alert people to the dangers of floating containers," said Mr Ryan.
The International Marine Organisation requires the master of a ship to report a lost container if it carries noxious substances.
But the only regulation for an empty container, or one holding non-poisonous substances, is that the master reports to the nearest coastal state if he comes across it.
Mr Ryan said the council wanted mandatory reporting of all lost containers, both in New Zealand and overseas.
Ships should be inspected when they arrived in port to check the number of containers on board.
Maritime Safety Authority deputy director Tony Martin said the problem was huge overseas, but estimated that only about one container a year was lost in New Zealand waters.
But Mr Ryan said container loss was such a growing problem worldwide that the Dutch Coastguard now had two vessels on permanent lookout.
One reason for the losses could be that some ships pile containers up to seven high, which may increase to nine high with the new generation of container ships.
Shipping companies often pay fewer port charges if their container loads are stacked high.
That can lead to a vessel becoming less stable in bad weather, making it pitch and roll and increasing the risk of losing cargo over the side.
It is estimated that at any given time there are five to six million containers in transit worldwide.
Most containers weigh two tonnes. They may sink if empty but bob below the surface for months if full.
