Ghost ship brought to life from the blackness of the sea

This sonar scan shows the entire length of the 155m Mikhail Lermontov, still intact two decades after it went to the bottom.

New technology has revealed a ghost-like image of the sunken cruise liner Mikhail Lermontov in the Marlborough Sounds.

Using sonar that works on a similar principle to ultrasound scanners that show fetuses in the womb, National Institute of Water and Atmospheric Research scientist Dr Ken Grange has captured new images of the ship showing the hull, funnel, cranes, bridge and decks.

Divers rarely see more than a small part of the 155m-long wreck because of poor visibility.

Dr Grange said the pale patches shown in the image above the front half of the wreck are schools of fish.

The ship, once the pride of the Russian cruise fleet, has lain on the sea floor at Cape Jackson at a depth of about 50m since the night of February 16, 1986, when it struck a rock in Port Gore Inlet and sank.

Of the more than 700 passengers and crew on board the 15-year-old vessel, only one crew member died.

Picton pilot and acting harbourmaster Captain Don Jamison made the decision to take the Lermontov through a passage never before used by ships of its size.

Dr Grange said Niwa bought the new sonar, which uses sound waves to produce digital images, to map shallow-water marine habitats.

It operates at a frequency of 675kHz and is mounted in a small torpedo-shaped "towfish" that is pulled along by a boat so it is just above the sea floor.

Raised objects bounce back sound waves which are processed into a digital signal and sent to a computer on the surface.

The Mikhail Lermontov is the third biggest diveable cruise shipwreck in the world.

Only the Empress of Ireland and the Titanic are bigger.

- additional reporting: NZPA