This paper describes the AmBot, a centipede-inspired amphibious robot for monitoring the Swan-Canning River, the most important estuary system in Western Australia. The major challenge in developing such a robot lies in that the limited physical size of the robot allows only one type of propulsion system to be used both on land and on water. This is in contrast to large amphibious robots that use wheels or track systems when on land and switch to propellers when on water. The focus of this paper is on the design of a single propulsion method suited to a small-sized amphibious robot. To achieve this, centipede-inspired tracks were engineered with each track-piece consisting of an aluminum base and a polystyrene-block float. It was hypothesized that tracks fixed with floats might be able to provide effective actuation both on land and on water for small-sized robots. When on water, the tracks provide propulsion force and buoyancy so that the waterline is well controlled. When on land, the tracks effectively spread the contact force across multiblocks, leading to effective actuation and low pressure on the sandy terrain, hence protecting the beach ecosystem. Finite element analysis (FEA) was applied to optimize the main components of the AmBot for weight reduction without sacrificing functionality and safety. The AmBot uses an Android-based remote-control system via the Internet, where the accelerometer, gyroscope, global positioning system (GPS), and camera on the Android device provide integrated navigation and monitoring sensing. A prototype was developed to validate the proposed design by conducting empirical studies.