This paper describes three different conceptual designs and its development, which could be used to form an autonomous underwater vehicle capable of swimming in different modes. Three prototypes have been constructed to mimic mainly anguilliform, labriform, and carangiform modes of swimming. For anguilliform mode, the body is designed with three segments made of flexible polyurethane, actuated and controlled by using shape memory alloy (SMA) wires. For labriform mode drag based propulsion, the initial design makes use of a rotating disk on which a planet gear rotates around a fixed sun gear. The model is able to achieve pectoral fin motions rowing, flapping and feathering in an integrated manner, with a single motor alone. For carangiform mode, the proposed design exhibits caudal fln propulsion. The caudal fln movements are realized by employing two motors, which achieves fln oscillation and caudal peduncle movement, respectively. A promising and interesting option could be to develop autonomous underwater vehicles by integrating the above three designs.