Mateusz Popek

Ostrów Lednicki was a centre of the Piast dynasty (tenth–fourteenth centuries AD), laying the foundations for the development of the Polish state. A collapsed tenth-century wooden fortification associated with Bolesław the Brave (the first king of Poland) and its unique sculptural element provide insights into early-medieval construction techniques.

This study presents a strong framework for the detection and classification of Submerged Cultural Heritage Assets (SCHA) in shallow marine environments using the integration of multibeam echosounder and airborne LiDAR bathymetry with object‐based image analysis and fuzzy logic–based classification. A total of 57 remote sensing anomalies at Puck Lagoon were identified and diver‐based ground‐truthed. Of these, 42% were confirmed as cultural heritage assets, for example, a World War II aircraft crash site, demonstrating the efficiency of the technique. The high‐dimensional feature space was diminished to two components explaining 61.7% of variance with principal component analysis, which revealed clear clustering of anthropogenic and nonanthropogenic objects. Random forest feature importance ranking and ANOVA F statistic test identified vector ruggedness measure and mean LiDAR intensity as the most discriminative features for automated classification. Application of fuzzy membership functions in knowledge‐based rules modelled overlapping feature values and measurement uncertainty, improving classification reliability. This technique extends the limits of nonintrusive underwater surveying and provides an open, methodological framework for heritage managers in shallow, protected marine environments, though site‐specific recalibration is required for transferability to contexts with differing depth, energy regime, substrate type or water clarity.

The focus of this article is to introduce the history of underwater archaeology in Poland until 1990. The chosen caesura corresponds to the profound systemic changes after the fall of communism in 1989. Tracing the history of underwater archaeology shows how the research methods of this subdiscipline has changed over six decades. Underwater archaeology has evolved from an amateur activity to a science with developed methods and methodology. In addition, the turbulent history shows the impact of acute historical events on the researchers' fate, including how deep a mark was left on scientists by World War II and the subsequent communist period. Scientific centres in Szczecin, Warsaw, Gdansk and Torun played an essential role in developing underwater archaeology in Poland. By the late 1980s and early 1990s, some centres of underwater archaeology in Poland had developed, and some had halted their activities. Despite many challenges and problems, underwater research has experienced dynamic growth and still holds an important place alongside other historical sciences.

Limited visibility in the underwater environment often restricts opportunities for archaeological prospection. Especially in reservoirs with a high content of suspended solids, methods based on acoustics prove to be extremely useful. This study represents the first high‐resolution acoustic mapping and archaeological prospections of the Old Oder Canal, which has extremely poor visibility. The study site is located near the town of Krosno Odrzańskie in Poland. The town is one of the country's most significant river crossings and settlements of mediaeval origin (including its wooden bridges). The following research objectives were identified: (1) exploration of the Old Oder Canal, including underwater acoustics and archaeological prospections; (2) analysis and interpretation of the study area based on acquired datasets; and (3) evaluation of secondary features of the river bathymetry for identification of archaeological objects. Possible locations of archaeological objects were determined based on analysis and interpretation of multibeam echosounder measurements of the riverbed. Fieldwork allowed structural elements of mediaeval bridges to be found and dendrochronological sampling performed. Feature selection analyses allowed the determination and evaluation of geomorphometric attributes, combining the characteristics of the discovered objects and diagnostics in order better to differentiate archaeological remains. Proposed secondary features may facilitate archaeological explorations in difficult environments.

Exploration of the marine environment using underwater remote‐sensing methods is the most reasonable method for investigating submerged archaeological heritage sites, preserving their current condition and maintaining them for future generations. While non‐invasive recognition of heritage sites is one of the main objectives of underwater archaeology, the nearshore environment of the small Polish town of Puck hides one of the biggest medieval harbours in the Baltic Sea. The following research objectives were met in this study: (a) exploration of underwater archaeological heritage harbour in Puck using high‐resolution hydroacoustics, 3‐D shallow seismics and underwater photogrammetry; (b) reconstruction of the submerged Puck medieval port by the combining of hydroacoustics, 3D shallow seismics, underwater photogrammetry and archival documentation; (c) estimation of the rate at which the bottom sediments containing the archaeological objects are being destroyed. The underwater archaeological site of Puck harbour was explored using multiple surveying methods, including multibeam echosounder, parametric sub‐bottom profiler, underwater photogrammetry, aerial photography and comparison with archival documentation. Very high‐resolution bathymetry from a multibeam echosounder allowed seabed features such as piles, stones and horizontal structural elements to be identified, along with other archaeological artefacts, boat wrecks and boat‐building artefacts. The 3‐D shallow seismic datasets allowed us to distinguish, for example, several outcropping structures, a previously unknown buried shipwreck, past excavation trenches, the harbour boundary and a palaeochannel of the Płutnica River. Fusing datasets from multiple sources in the geographic information system (GIS) environment allowed for a combined visualization of the heritage sites, providing a broad archaeological demonstration of the underwater structure. By comparing with archival documentation, we calculated that 43% of biogenic layers containing archaeological objects eroded over 26 years. Our results demonstrated that without any doubt, underwater remote‐sensing methods are the most appropriate for exploration and investigation of underwater heritage sites while maintaining their original value.