  We describe a docking mechanism and strategy to allow modular self-assembly
for the Modboat: an inexpensive underactuated oscillating swimming robot
powered by a single motor. Because propulsion is achieved through oscillation,
orientation can be controlled only in the average; this complicates docking,
which requires precise position and orientation control. Given these
challenges, we present a docking strategy and a motion primitive for
controlling orientation, and show that this strategy allows successful docking
in multiple configurations. Moreover, we demonstrate that the Modboat is also
capable of undocking and changing its dock configuration, all without any
additional actuation. This is unique among similar modular robotic systems.
