We describe an interaction paradigm for controlling
a robot using hand gestures. In particular, we are
interested in the control of an underwater robot by an onsite
human operator. Under this context, vision-based control
is very attractive, and we propose a robot control and
programming mechanism based on visual symbols. A human
operator presents engineered visual targets to the robotic
system, which recognizes and interprets them. This paper
describes the approach and proposes a specific gesture language
called "RoboChat". RoboChat allows an operator to control a
robot and even express complex programming concepts, using
a sequence of visually presented symbols, encoded into fiducial
markers. We evaluate the efficiency and robustness of this
symbolic communication scheme by comparing it to traditional
gesture-based interaction involving a remote human operator.