Page last updated at 01:45 GMT, Wednesday, 1 October 2008 02:45 UK

Underwater view of high tech propeller

Propellers are typically one of the noisiest parts of any craft, but these are built to be as quiet as possible.

This minimises the impact on the whales being studied and prevents interference with monitoring equipment.

Although the propeller is relatively quiet it does generate a lot of drag, slowing the boat down when under sail.

It is also designed to reduce injury to marine life in the event of a collision.

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