Holding a Steady Course

Rob White reports

After final technical checks - no point in getting hundreds of miles out and finding something doesn't work - the dive ship Northern Horizon set sail from Cork at 11 o'clock in the evening of Sunday 1st July.

The side scan sonar is lifted

We woke next day to find her holding a steady course, steaming at 10 knots over a gently rolling grey sea. Northern Horizon's Captain Keith Herron is pleased with the project so far. "Well on target for our first dive" he told me, as his ship rose and fell gently to the North Atlantic swell. Earlier in his watch he'd seen two whales, but now the sea was empty apart from a lone Spanish fishing boat.

As the sun broke through, first task of the day was to film Northern Horizon herself. The 'Rib' - rigid inflatable boat - was launched and director Gary Johnstone and cameraman Mike Robinson took to the water, speeding round the ship to get the best angles they could find. No easy task because however gentle the waves may seem from on board ship, at sea level the Atlantic is a much rougher customer.

David Mearns and Jim Mercer study the sonar

Then came one of the first key tests for Search Director David Mearns - a deepwater dive for the towfish. Soon this 'Sidescan Sonar' will make the first contact with Hood for 60 years - its electronic pulses probing deep into the ocean to find the giant warship's last resting place. As the ship's computer-controlled thrusters kept her on a steady course at 2 knots, the towfish tracked the ocean bed 1500 metres below. Mearns watched its every move intently. Finally he stood back, relieved. "The sonar looks terrific," he said "...but we'll have to tweak the suroodface computer a bit. But it'll be OK."