A logical extension to the large-scale archaeological prospection of entire landscapes, as postulated and exemplified by the LBI ArchPro, is the inclusion of wetlands and underwater archaeological landscapes. Using remote sensing methods in the form of acoustic measurement methods (e.g. side scan sonar, multi-beam sonar, sub-bottom profiler, boomer, pinger) but also underwater magnetometers or GPR operated from the water surface or from submersible rovers on or near the sea floor, it becomes possible to map archaeological heritage underwater or buried in the sediments of lakes, rivers and marine environments. Airborne Laser Bathymetry, already successfully demonstrated by the LBI ArchPro, is ideally suited, under suitable visibility conditions, to contribute to the efficient mapping of submerged structures of archaeological interest. Sites with great relevance for the combination of terrestrial large-scale archaeological prospection and new developments in efficient underwater prospection methods range from currently investigated alpine Neolithic and Bronze Age lacustrine settlements, Etruscan settlements at Lake Bolsena found at water depths down to 10 m, to Antique settlements submerged along the coastlines of the Mediterranean and Viking Age harbours related to current Norwegian and Swedish case studies. The remains of harbour constructions and fortifications, submerged architecture and shipwrecks are an important and endangered part of our cultural heritage, which from an integrative perspective need to be considered, addressed and included in order to permit a holistic understanding of archaeological landscapes and seamless landscape archaeology.