  In the last few years, there have been many new developments and significant
accomplishments in the research of bionic robot fishes. However, in terms of
swimming performance, existing bionic robot fishes lag far behind fish,
prompting researchers to constantly develop innovative designs of various
bionic robot fishes. In this paper, the latest designs of robot fishes are
presented in detail, distinguished by the propulsion mode. New robot fishes
mainly include soft robot fishes and rigid-soft coupled robot fishes. The
latest progress in the study of the swimming mechanism is analyzed on the basis
of summarizing the main swimming theories of fish. The current state-of-the-art
research in the new field of motion coordination and communication of multiple
robot fishes is summarized. The general research trend in robot fishes is to
utilize more efficient and robust methods to best mimic real fish while
exhibiting superior swimming performance. The current challenges and potential
future research directions are discussed. Various methods are needed to narrow
the gap in swimming performance between robot fishes and fish. This paper is a
first step to bring together roboticists and marine biologists interested in
learning state-of-the-art research on bionic robot fishes.
