They ordered him to give the Kaiko Maru free passage, and he reluctantly complied.

NEWYORKER: Neptune��s Navy

As the Hunter and the Kaiko Maru negotiated the floes, they smashed into each other.

NEWYORKER: Neptune��s Navy

As a result of limitations like these, he said, the Japanese craft Kaiko had limited manoeuvrability and needed a custom-built ship for spooling out the reams of heavy cable required to attach it to the ship.

BBC: Robot sub aims for deepest ocean

While manned exploration had until now seen a 52-year hiatus, scientists have used two robotic unmanned vehicles to explore the Mariana Trench: Japan's Kaiko made a dive there in 1995 and the US-based Woods Hole Oceanographic Institution's vessel Nereus explored the deep in 2008.

BBC: James Cameron back on surface after deepest ocean dive