Cook Strait is a notorious stretch of water and, as many ferry passengers know, it can be a frightening stomach- churning ride.
It's a rough patch of sea with fierce tides. Thirty-knot winds are routine, it can get up to 80 knots and waves get up to 7 metres - the height of a two-storey house.
Fortunately for landlubbers, the rough bit of the passage between Wellington heads and Tory Channel lasts only about an hour.
But for a small cadre of seamen this is their patch and they are out there day and night in all weather, 365 days a year, in the Seapatroller, a 27m converted old navy inshore patrol boat.
Their job is to patrol the cable protection zone, a 7-kilometre-wide strip running 40km from Oteranga Bay, on Wellington's southeastern extremity, to the nearest convenient South Island landfall at Fighting Bay.
The Seapatroller has a crew of three at a time - crew work a two-week-on and two-week-off roster. Their job is to be ever vigilant.
During four-hour watches, they keep their eyes peeled for any boats that are a potential threat to the cables.
This could be by dropping an anchor, dragging a net or even dangling a fishing line that could break, damage or even just snag New Zealand's most vital power and telecommunication lifelines.
The three Transpower power cables and four telecommunication cables are expensive but vulnerable and a careless boatie could wreak havoc, says Seapatroller skipper Ken Bedford, who has been on the strait for 10 years.
He is out there for two weeks at a time, sharing the lookout with two other crew, and he seems to have lost none of his love of the sea or his commitment to making sure the cables aren't damaged.
"You have to keep paying attention and looking because the strait is constantly changing and there are vessels coming and going all the time.
"So you're always going ‘Who is that?' - our job is to be nosy and know what everybody is doing, who they are, what they're doing and why."
Even in the middle of the night one crewman is always on watch, ready to call up a vessel and, if necessary, warn them off.
"A yacht that sinks and lands on the cable could easily ruin it - and a lot of vessels sink out there - so if a vessel starts to founder we want to be there to help them pump it out or tow them away from the cable zone."
But trawlers were the biggest threat and just a few weeks ago they ordered a trawler that was approaching the cable zone to turn around.
Penalties are steep for damaging a cable - forfeiture of the vessel and fines of up to $250,000.
The most crucial cables across the strait are Transpower's, which carry up to a third of the North Island power supply. It would cost $90 million to lay a new power cable or $15m to replace a communications cable.
The last major incident was in 1991 when a fishing trawler snagged a communications cable and broke it.
Mr Bedford said a key part of the job was educating seafarers. Catching people was just a small part of the job and prosecution was always a last resort. Just in case, they kept a database of nearly 1000 vessels that have approached over the years, so errant skippers cannot plead ignorance. Fairfax NZ
- The Marlborough Express