Advances in engineering design and modelling have enabled modular build to play an important part in accelerating production of recent classes of submarine. However, this is typically limited to large structural modules (such as Pressure Hull sub-units) or partially outfitted internal rafted modules that are not designed to be removed upon completion of build. Capability upgrades through life generally require significant modifications within maintenance periods which increase maintenance programmes and negatively impact availability of assets. Platforms with fully outfitted modules that can be readily attached and detached through life could open the door to a host of additional maintenance and overhaul options to increase efficiency, reduce cost and improve and diversify capability. The Bridge Fin is a critical part of the submarine design, linking the internal environment with the external world. The Bridge Fin structure provides protection for a wide variety of systems, allowing the crew to maintain situational awareness and capability whether surfaced or submerged. Due to the complex nature of the systems within the Bridge Fin, the structure and equipment within requires frequent survey, maintenance and upgrade. Coupled with increasing demand on hydrodynamic efficiencies and a reduction in Bridge Fin spatial envelopes means that designs are becoming more complex with increased build and supportability burdens. At both build and in-service points there are increasing issues with accessibility for installation and repair of both structure and systems. This paper explores whether there are potential benefits associated with a modular Bridge Fin design throughout the build and in-service phases in both current and future submarine designs.