It seemed a bit of a joke in the press, as they reported that a bulk carrier had been asked to leave New Zealand waters because of a dirty bottom. Then she was banned from Fijian waters too, which became a bit more serious, leaving the ship operators obviously wondering where they could take their vessel for a legal scrub of the barnacles and tube worms that had so alarmed the New Zealand authorities.

A couple of hundred years ago, energetic mariners would rig up a big coir mat and with half the crew on the port rail and the other half to starboard, they would drag the mat back and forth under their ship, to remove the marine growth that would have been slowing them down to a crawl. Sadly, no such strategy was available to the modest crew of the 33,500 dwt DL Marigold, which will now go down in marine history as the first victim of such a rejection.

But it is a salutary reminder that this is yet another environmental issue which has been boiling away for hard-pressed ship operators, to add to the hard decisions on ballast water systems and how to control all the various atmospheric emissions. Just slap a coat of anti-fouling on the underwater hull and forget it to the next dry-docking? That is a policy for the past, since the 2011 IMO “Guidelines for the control and management of ships’ biofouling to minimise the transfer of invasive aquatic species” was published, and in the intervening years, quietly creeping up on the industry. May 2018 marks the date when these rules, which the New Zealanders have “promoted” from mere guidelines, come into force, but their Ministry for Primary Industries is now empowered to take action in cases of “severe” biofouling.

How severe must severe be before the divers surface and demand that a ship leaves port forthwith? Years ago, I was in a drydock in Singapore, where a tanker that had been laid up for several years was being cleaned prior to reactivation. There were tons and tons of long goose-necked barnacles being scraped off the bottom of this ship, to be collected up in a stinking mass, along with the weed that had grown on the vertical surfaces. They were using a bulldozer to put it in great skips for disposal, but it was not a job for the faint-hearted.

You don’t think of Port State Control frogmen routinely inspecting the underwater parts of the ship, at least not until now, but fouling is just one more bureaucratic hurdle to be surmounted, with its own certification regime, record books and “management plan” to be revealed to the questing authorities.

The waters around New Zealand are beautiful and clear and the authorities obviously want to keep them that way. And if the operators of the bulker thought that they could get the underwater cleaners to work, once the ship was sheltering inside the reefs of Fiji, they were quickly appraised of the unacceptability of that plan. Rolling around in a long Pacific swell far from land is not a suitable location for a scrub, so a visit to a dry dock would seem to be the most likely (if more expensive) solution.

These may only be IMO Guidelines, but look for this more prescriptive interpretation by other countries sooner rather than later. In New Zealand, the definition of “severe” is quite explicit – either the vessel has a 40% coverage of barnacles or tube worms over a continuous portion of the hull more than 4m in length, or if any anemone, bivalve, crustacean, sponge, sea snail, sea squirt, sea star or marine worm is present, you better make arrangements for a rapid departure.

It makes you wonder whether a marine biology module ought to be added to the statutory certification of a ship master. After all, do you categorically know that, before you arrive in a port after a long passage, that your bottom is clean, your sea valves and intakes unsullied by marine growth? How on earth would this be established? There is some money to be made in underwater hull inspection and the provision of frogpersons, that’s for sure.