Masonry bridges are among the most sustainable structures ever to have been built. The long service time, the resilience to carry larger loads than originally intended, and significantly lower life cycle cost compared to other bridge types suggest that we should consider the design and construction of new masonry bridges, even if their initial cost is greater than that of steel or concrete bridges The aim of this work is to understand the structural behaviour and study the collapse of a single-span masonry hydrostatic shell, that is a shell designed specifically to carry a hydrostatic load. Due to the complexity of the masonry shell interacting with fill, it is necessary to use a combination of computational methods and load tests on physical models in their structural assessment. We perform a load test to failure on a physical model spanning 770 mm made from 3D printed blocks and analyse the model using the Discrete Element Method (DEM) in Dassault Systemes Abaqus. ` The physical model behaved well and predicts that the bridge could be used at full scale. The preliminary results from a computational DEM model are found to be qualitatively good, but greatly overestimate the collapse load of the bridge.