Abstract: A comprehensive review on bio-inspired fish robots has been done in this article with an enhanced focus on swimming styles, actuators, hydrodynamics, kinematic-dynamic modeling, and controllers. Swimming styles such as body and/or caudal fin and median and/or paired fin and their variants are discussed in detail. Literature shows that most fish robots adapt carangiform in body and/or caudal fin type swimming as it gives significant thrust with a maximum speed of 3.7 m?s?1 in iSplash-II. Applications of smart or soft actuators to enhance real-time dynamics was studied from literature, and it was found that the robot built with polymer fiber composite material could reach a speed of 0.6 m?s?1. However, dynamic modeling is relatively complex, and material selection needs to be explored. The numerical and analytical methods in dynamic modeling have been investigated highlighting merits and demerits. Hydrodynamic parameter estimation through the data-driven model is widely used in offline, however online estimation of the same need to be explored. Classical controllers are frequently used for navigation and stabilization, which often encounters the linearization problem and hence, can be replaced with the state-of-the-art adaptive and intelligent controller. This article also summarizes the potential research gaps and future scopes.

Key words: biomimetic fish robot, swimming modes, hydrodynamic modeling, motion control, smart actuators