This paper describes an underwater walking robotic system being developed under
the name AQUA, the goals of the AQUA project, the overall hardware and software
design, the basic hardware and sensor packages that have been developed, and
some initial experiments. The robot is based on the RHex hexapod robot and uses
a suite of sensing technologies, primarily based on computer vision and INS, to 
allow it to navigate and map clear shallow-water environments. The sensor-based 
navigation and mapping algorithms are based on the use of both artificial
floating visual and acoustic landmarks as well as on naturally occurring
underwater landmarks and trinocular stereo.