Media playback is unsupported on your device Media caption The BBC's David Shukman: "We are now entering a new era of almost constant observation of the oceans"

A fleet of marine robots is being launched in the largest deployment of its kind in British waters.

Unmanned boats and submarines will travel 500km (300 miles) across an area off the southwestern tip of the UK.

The aim is to test new technologies and to map marine life in a key fishing ground.

In total, seven autonomous machines are being released in a trial heralded as a new era of robotic research at sea.

Two of the craft are innovative British devices that are designed to operate for months using renewable sources of power including wind and wave energy.

The project, led by the National Oceanography Centre, involves more than a dozen research centres and specialist companies.

Drones of the deep Marine robots come in a variety of strange shape and sizes, and no fewer than four different types are being deployed in this project, part of a new generation of devices designed to make marine research far cheaper and easier than with large crewed vessels. Autonaut: Powered by wave action and solar panels, Autonaut looks like a canoe with an aerial on top. It bobs on the surface and provides a platform for instruments. The result of a partnership between a management consultant and a former Royal Navy commodore, Autonaut was designed and built by MOST in Chichester. C-Enduro: Distinctively shaped with an in-built wind turbine reminiscent of an air-boat, C-Enduro is designed to operate on its own for up to three months. A diesel motor provides back-up power. Instruments record water and weather data, and a winch can lower sensors below the surface. The machine is designed and built by ASV in Portchester in Hampshire. Waveglider: The Waveglider involves twin elements, one floating on the surface, the other being a system of miniature blades dangling underwater and harvesting energy. Billed as ideal for operating "for years at sea with no fuel, emissions or crew", the US makers have now turned out more than 100 units. Slocum Glider: Named after Joshua Slocum, the first solo round-the-world sailor, this American device looks like a torpedo. It dives and rises through the water with a system of variable buoyancy. Every time it surfaces, the glider can relay information by satellite and pick up new instructions.

Chief scientist Dr Russell Wynn told BBC News: "This is the first time we've deployed this range of vehicles carrying all these instruments.

"And it's exciting that it's the first time we can measure everything in the water column and all the life in the ocean simultaneously.

"The ability to measure the temperature or the weather at the ocean surface, or dolphins and seabirds with the cameras on the vehicles - no-one's ever been able to do that at the same time hundreds of miles from the shore."

Data about the oceans is usually gathered by a combination of satellites, buoys and research ships, but all three have limitations in their coverage, and large crewed vessels are particularly expensive.

The motivation for exploring the use of massed robotic vehicles is to assess whether they can provide near-constant coverage at far lower cost - the equivalent of CCTV offering round-the-clock surveillance.

The target for the deployment is an area of ocean marking the boundary between Atlantic waters and tidal waters from the English Channel - what's known as an ocean front.

Fronts like this usually create upwelling that brings nutrients from the seabed towards the surface and encourages plankton to thrive. That in turn attracts fish, whales, dolphins and porpoises.

Most of the craft are being deployed from the Isles of Scilly for a three-week traverse of the ocean. The exact route of the journey is being withheld to avoid the risk of anyone interfering with the experiment.

Instruments will record key parameters of the ocean, ranging from the concentrations of plankton to the clicks and whistles of dolphins and porpoises. Cameras on the surface vehicles will also attempt to capture images of seabirds and other marine life.

According to Dr Wynn, the UK's 700,000 sq km of waters are highly productive as fishing grounds but the processes at work in them remain unclear.

Image caption The UK government has identified robotics as one of the "eight great technologies"

"Actually understanding how that sea works and how the animals are distributed is a real challenge if you've only got a small number of ships and a few buoys dotted around.

"Having a fleet of vehicles that can go out, without humans on board, controlled by satellite, really gives us a chance to transform our ability to monitor the ocean.

"At the moment a lot of decisions about how we manage the oceans are based on very few data - relatively simple things like where do dolphins and seabirds go to feed? We actually have very little information on that."

Until now, companies developing robotic vehicles for use at sea have focused on military and commercial customers such as the US Navy and oil and gas companies, and American firms have dominated the market for automated submarines.

The British government's hope is that the UK may become a leader in unmanned surface machines - robotic boats - which can act as drones gathering information to help weather forecasters or do conservation work.

Ministers have identified robotics as one of the "eight great technologies" that can help rebalance the country's economy and drive growth.

Funding has allowed the National Oceanography Centre to support two UK companies, MOST and ASV, in developing their AutoNaut and C-Enduro robotic boats that are on trial now.

The first phase of the deployment is planned to end in three weeks' time, when the vehicles will be retrieved from the ocean and the results analysed.

Partners in the project include the universities of St Andrews and Exeter, Cefas, the Marine Biological Association, Plymouth Marine Laboratory, the British Oceanographic Data Centre, British Antarctic Survey, UK Met Office, Royal Navy and DSTL. Corporate partners include MOST, ASV, J&S, RS Aqua and Liquid Robotics.