Subaqueous landslides are a major class of underwater slope instabilities that pose significant hazards to coastal regions and offshore infrastructure. These events are characterized by very large deformations, complex failure mechanisms, and strong sensitivity to geometric and geomechanical parameters. Experimental investigation of such processes is severely limited by scaling effects, material complexity, and the extreme spatial and temporal scales involved, making numerical simulation a primary tool for their analysis. This work presents an Eulerian finite element framework for the large-deformation modeling of subaqueous landslides. In contrast to conventional Lagrangian formulations, which suffer from severe mesh distortion under large strains, the Eulerian approach employs a fixed spatial mesh through which material flows, enabling stable and robust simulation of progressive failure and post-failure evolution. The framework is formulated within a continuum mechanics setting and is compatible with advanced constitutive models for geomaterials. The capabilities of the Eulerian framework are demonstrated through numerical simulations of representative subaqueous landslide scenarios, including interaction with offshore infrastructure. The results highlight the effectiveness of Eulerian finite element formulations as a computationally robust and versatile tool for large-deformation geomechanics and slope disaster analysis.