They said the glider had crisscrossed the 13,000-foot-deep Virgin Islands Basin between St. Thomas and St. Croix more than 20 times since it was launched in December.

And it could keep going on its own for another six months, predicted the team from the Woods Hole Oceanographic Institution, which is on Cape Cod, and Webb Research, a company based in Falmouth, Mass.
"Gliders can be put to work on tasks that humans wouldn't want to do or cannot do because of time and cost concerns," Dave Fratantoni of Woods Hole said Thursday. "They can work around the clock in all weather conditions."

Such a robot can carry sensors to measure temperature, salinity, and biological productivity.

The glider surfaces from time to time to fix its positions using the Global Positioning System and to communicate via Iridium satellite to a laboratory on the shore.

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