SILVER is a four-legged underwater vehicle. Each leg is based on a crank-slider mechanism with a serial spring, and two rotational joints at the hip (3 DoF each leg). Twelve Dynamixel AX-12a smart servomotors are connected in daisy chain, and powered by a LiPo battery for an average autonomy of 2 hours. The structure in PVC can hold sensors such as cameras, laser scan, salinity, pressure and temperature sensors, etc., or it can mount robotic arms or grippers. Matlab controllers, running on an external (out of water) laptop, enable SILVER with hopping, walking and crawling gaits.The self-stabilizing gaits, the reduced disturbances induced on sand during locomotion, and the peculiar underwater capability grants to the robot unique features for the investigation of seabed or for the study of legged locomotion in reduced gravity environment.