Simulates sea-level rise and fall from raster-based elevation models through functions for relative vertical datum transformation of Digital Terrain Models (DTMs) and integration with bathymetric data to produce continuous terrestrial–marine Digital Elevation Models (DEMs). Supports coastal exposure modeling, paleogeographic reconstruction, submerged landscape analysis, and climate change impact assessment. Optional gap-filling and threshold-based terrain filtering facilitate reconstruction of incomplete elevation surfaces and scenario-based landscape simulation. Applications span coastal engineering, geomorphology, archaeology, environmental modeling, and geospatial analysis.