An untethered, fully automated submersible platform capable of performing underwater tasks and missions with on-board sensor, navigation and payload equipment is known as unmanned underwater vehicle (UUV) or autonomous underwater vehicle (AUV). UUVs continue to serve diverse roles in ocean sensing, surveillance, and engineering. Valuable and exacting tasks are presently being performed by UUVs and a continued growth of underwater missions is envisioned in the near future as vehicles become more capable and less expensive. UUVs have a wide range of applications, from oceanographic studies, and underwater acoustic imaging and communications to infrastructure monitoring and surveillance operations. UUVs continue to see increased use in diverse scientific, commercial, and education sectors. For the purpose of education and basic research academic institutions have likewise developed open source UUV architectures (McCarter, et al., 2014) that allow for complete control of the vehicle's functionality. This thesis describes the design, development and in-house fabrication of a fully scalable, modular and open-source UUV at the College of Engineering in University of Massachusetts Dartmouth. The open-source features allow the users and operators to tailor sensor suite and architecture to diverse UUV missions. The UUV provides a scalable and expandable sensor suite. The modular design and scalability of the vehicle provides a platform for expansion of research efforts in numerous blue economy fields spanning diverse areas from underwater acoustic communication, and surveillance to navigation, and control of the UUV. The vehicle provides an open-source programming environment for mission planning and post mission diagnostics. This UUV will form the backbone for testing ecologically friendly underwater acoustic signaling schemes that greatly reduce anthropogenic noise and interference.