SOMETHING unusual is swimming in the sea near the United States Virgin Islands. It has been there since December, slowly criss-crossing the 65km between St Croix and St Thomas, periodically surfacing and then diving back down again to depths of 4,000 metres. It is likely to keep this up for another three or four months. It is not some strange aquatic creature, but a new robotic underwater vehicle that could revolutionise the way oceans are studied. - The EconomistThis interesting little machine is called a Slocum, "after Joshua Slocum, who in 1898 was the first person to sail single-handedly around the world." It's pretty cool this entire machine is driven by mechanical energy produced by oil, wax, compressed air, and buoyancy. The change in temperature of the water causes the wax and oil to affect the buoyancy of the machine, which allows it do either dive or rise. The Slocum does use a little bit of battery power, but it is very minimal since it does not carry any passengers.
This idea has been around since 1980, but this is the first time it is expected to travel for 2-3 years. The Slocum measures the salinity and many other things from the water, which may be useful to determine the effect of Global Warming on the ocean.
I believe Dr. Webber had mentioned something about the temperature difference in the water and how we could possibly use that temperature change to make energy. Although this idea has been around for almost thirty years, maybe this is the first step to development of new technology in that direction.