Underwater vehicles have been developed mainly for underwater exploration and rescue. Many large- and middle-size vehicles are available but few are in smaller scale. As the size goes into mini-scale which is less than 20 cm, it is challenging to allocate required components within limited space, while providing designed functions at the same time. The aims of this research are to design and rapid manufacture structural components for a remote-controlled underwater vehicle in the mini-scale region. The vehicle would integrate vision capability to provide functions of underwater ecological observation and tracking. In order to design the structural components for this mini-scale vehicle, commercial CFD software was adopted to simulate flows. An improved external shape was obtained and detailed designs of the structural components were implemented. A rapid prototyping technique, Shape Deposition Manufacturing (SDM) process, was utilized to rapidly manufacture these components. The finished components were assembled with control modules and propulsion systems as an underwater vehicle and the preliminary underwater test was conducted successfully.