  There exists a capability gap in the design of currently available autonomous
underwater vehicles (AUV). Most AUVs use a set of thrusters, and optionally
control surfaces, to control their depth and pose. AUVs utilizing thrusters can
be highly maneuverable, making them well-suited to operate in complex
environments such as in close-proximity to coral reefs. However, they are
inherently power-inefficient and produce significant noise and disturbance.
Underwater gliders, on the other hand, use changes in buoyancy and center of
mass, in combination with a control surface to move around. They are extremely
power efficient but not very maneuverable. Gliders are designed for long-range
missions that do not require precision maneuvering. Furthermore, since gliders
only activate the buoyancy engine for small time intervals, they do not disturb
the environment and can also be used for passive acoustic observations. In this
paper we present ReefGlider, a novel AUV that uses only buoyancy for control
but is still highly maneuverable from additional buoyancy control devices.
ReefGlider bridges the gap between the capabilities of thruster-driven AUVs and
gliders. These combined characteristics make ReefGlider ideal for tasks such as
long-term visual and acoustic monitoring of coral reefs. We present the overall
design and implementation of the system, as well as provide analysis of some of
its capabilities.
