On a white sand beach tucked between gleaming upscale resorts along the west coast of Barbados, a group of sunburned computer scientists, graduate students, and technicians look on intently as a small canary-yellow robot ambles up and down the beach. A few curious beachgoers soon join them. “Looks rather lovable, doesn't it?” a British tourist remarks.

The robot is more than just lovable. With six rotating flippers, three on each side of its boxy metal carapace, this machine is amphibious, capable of both walking and swimming—an attribute that is unique in the robot world. As more onlookers gather, the little robot heads out through the surf and disappears into the turquoise waters that surround this Caribbean island.

Photo: McGill University Mobile Robotics Lab

Bot's Night Out: One of the authors, Gregory Dudek [left], helped by Robert Sim, tests Aqua's ability to walk from the beach into the water. The night work came after a long day of fine-tuning during one of the team's trips to Barbados.

The mechanical hexapod, called Aqua, is the latest in a series of seagoing robots our research group at McGill University, in Montreal, has been developing in collaboration with teams led by Michael Jenkin at York University, in Toronto, and Evangelos Milios at Dalhousie University, in Halifax, N.S., Canada. Our goal is to develop an underwater vehicle that can autonomously explore and collect data in aquatic environments while surviving the harsh saltwater conditions and often turbulent waters of the open sea. In building Aqua, we are tackling one of the most challenging topics in robotics: integrating vision and locomotion into an amphibious machine that can determine what it is “seeing,” where it is, and where it is going.

But more than just providing an interesting engineering exercise, Aqua, we hope, will someday play an important role in protecting coral reefs. The most biologically diverse and sensitive components of the world's marine ecosystems, coral reefs are extremely fragile, and today they are in a state of crisis around the globe. Twenty percent of the world's reefs have already been destroyed, mainly as a result of human activity. The remaining reefs urgently require protection. As our preliminary experiments in Barbados showed, underwater robots such as Aqua could help conservationists monitor the health of reefs and thus be in a better position to protect them.

In the past 30 years, marine scientists have come to rely on underwater vehicles, or UVs, to probe ocean depths that before were largely inaccessible to humans. Often, these vehicles reveal details about the ocean that couldn't be obtained using data-gathering instruments deployed on ships or satellites.

For instance, at the Massachusetts Institute of Technology, in Cambridge, the Deep Water Archaeology Research Group has been using a robotic UV to create precise photomosaics of under water archaeological sites. Researchers at the Scripps Institution of Oceanography, in La Jolla, Calif., and at the Woods Hole Oceanographic Institution, in Massachusetts, have been experimenting with ocean robots to gather data on hurri canes and marine life. Also, a consortium of Canadian and U.S. universities is developing robotic crawlers to keep tabs on environmental conditions in the Pacific Ocean [see “Neptune Rising,” IEEE Spectrum, November 2005].

Unlike many earlier UVs, Aqua is intended for shallower waters, and its design reflects this. Although the majority of UVs are large and unwieldy—some require a crane to lower them into the water—Aqua measures only 50 by 65 by 13 centimeters and weighs just 18 kilograms. Aqua is thus easier to deploy: you can literally throw it into the water, or it can launch itself from the beach [see photo, “Bot's Night Out”].

The robot is also incredibly maneuverable. Most UVs are propeller-driven, so the range of actions they can execute is fairly limited. Aqua's flippers move independently, enabling it to move forward, backward, up, down, and sideways; it can swim in a straight line or along a sinusoidal or helical path, and it can perform tight somersaults and rolls [see slideshow below, “The Life Aquatic”]. Using six flippers instead of four also helps stabilize the robot when it's performing such tasks as recording video in rough waters.