The underwater robot is a basic tool to explore the unknown territories in the underwater region of the coastal areas and oceans, both from the scientific and industrial perspectives. With the aim of developing an efficient and environmentally friendly underwater robot, a Squid-like robot with two undulating side fins has been developing for many years by the authors' group in Osaka University, Japan. The high ambitious project started in 2002; from then different models have been developed to reach the goal of achieving a high-performance underwater vehicle. The body and propulsion system of the robot have been developed by following the swimming mechanism of flat-fishes that use undulating side fins, e.g. Squid, Stingray Cuttlefish and Manta. The Squid-robot is now in its fifth generation of development. In the present paper, the review of the development of models of the Squid-robot is presented. The development of the mechanical system and the control system of each model is described in brief. Some CFD computations and motion simulations of Model-4 are also discussed. The background of developing a new model and the updated features are stated for each model respectively. The future target of development of the robot is also pointed out. The objective of this paper is to provide relevant and useful information to the engineers involved in underwater vehicle design, and for those with an interest in the fast-growing area of biomimetic swimming robots.