Traditional ROV's and underwater robots are based on propeller/thruster/control surface designs. 
Although these traditional mobiltiy mechanisms work well, they limit the operatiaon of the vehicle to the
open water. In contrast the AQUA robot 'swims' using 6 paddle-link legs. By driving its legs in different
gaits, a high level of mobility is obtained in both free swimming and surface swimming modes. In
addition, legs can be used to propel the vehciel ina walking gait, permitting the vehicle to walk into the 
sea and to walk along solid surfaces under water. Currently two different sets of legs are used for 
swimming and walking gaits, although a common set of legs for both modes of locomotion are in 
development.

The AQUA robot is visually guided. In addition to onboard video capture for teleoperation, a trinocular 
vision/inertial sensor pod, and acoustic localization systems have been developed for the robot. The 
trinocuarl vision vision/inertial sensor pod is used to develop a 3D model of the robot's environment, 
while the acoustic localization system utilizes a surface-based acoustic array to localize the robot based 
on an active acoustic source on the vehicle.

This talk introduces the AQUA project, including its locomotive, sensing and reasoning strategies. 
Technical details of the robot will be presented along with results form the robot's sea trials held at the 
Bellairs Marine Research Institute in January 2004.