Croatia has a long history of underwater archaeological research, especially of shipwrecks and the history of sea travel and trade in Classical Antiquity, but also including intermittent discoveries of submerged prehistoric archaeology. Most of the prehistoric finds have been discovered by chance because of construction work and development at the shore edge or during underwater investigations of shipwrecks. Eustatic sea-level changes would have exposed very extensive areas of now-submerged landscape, especially in the northern Adriatic, of great importance in the Palaeolithic and early Mesolithic periods. Because of sinking coastlines in more recent millennia, submerged palaeoshorelines and archaeological remains of settlement activity extend as late as the medieval period. In consequence, the chronological range of prehistoric underwater finds extends from the Mousterian period through to the Late Iron Age. Known sites currently number 33 in the SPLASHCOS Viewer with the greatest number belonging to the Neolithic or Bronze Age periods, but ongoing underwater surveys continue to add new sites to the list. Systematic research has intensified in the past decade and demonstrates the presence of in situ culture layers, excellent conditions of preservation including wooden remains in many cases, and the presence of artificial structures of stone and wood possibly built as protection against sea-level rise or as fish traps. Existing discoveries demonstrate the scope for new research and new discoveries and the integration of archaeological investigations with palaeoenvironmental and palaeoclimatic analyses of submerged sediments in lakes and on the seabed. A major challenge for the future is to develop better procedures for the integration of scientific research, commercial and industrial development, and the management and protection of the underwater heritage.

In September 1967 an important shipwreck site was discovered near the islet of Gnalić in Northern Dalmatia (Croatia). It immediately raised significant interest in the scientific community and the broader public. Due to logistical and financial issues, the excavation ceased after five short-term rescue research campaigns, over a total duration of 54 working days. Renewed interest in the site, particularly the hull remains, resulted in reviving the project after 45 years. The trial campaign, carried out in 2012, had a positive outcome, and the excavation has continued annually in a systematic way. The nature of the site demanded significant effort to document the excavated areas. Considering all the temporal restrictions caused by various reasons, photogrammetry proved to be an extremely helpful and efficient tool.

The remains of ancient ships from various time periods are commonly found on land and under the sea in conditions that make it difficult to reconstruct their original form and structure. For this reason, the reconstruction should be supported by other data, such as data on similar ships, but also by certain assumptions. The results of the reconstruction are significant not only in a historical sense but are of exceptional importance when building floating replicas. Two ships, Nin 1 and Nin 2, today for promotional purposes known as Condurae Croaticae, were found in Nin (Croatia) at the end of the 1960s. They are about 8 to 10 m long, and tentatively dated to the 11th century AD, although there are indications that they could be dated two centuries later. Based on archaeological finds exhibited in the Museum of Nin Antiquities, hull line drawings were created, according to which two floating replicas were made at the end of the 1990s. Considering the problem of hogging that appeared in both ships, a new proposal for the reconstruction of the original hull lines was performed based on the available documentation. The aim of this paper is a systematic analysis of its calm water resistance. Based on the established credibility of experimental testing, a scale model (1:4 ratio) of the Nin 1 vessel is constructed and evaluated through towing tank experiments. The second approach, the CFD method, is a reliable numerical method for calm resistance estimation, but it is rarely used in the analysis of ancient ships. Finally, the widely used empirical Holtrop method is also applied, but it was developed for ships of larger dimensions and with large parts of flat bottoms and, therefore, the more appropriate Delft Hull Yacht Series method is also tested. The results obtained by applying the four mentioned methods are compared and discussed.

Krajem šezdesetih godina 20. stoljeća na ulazu u ninsku luku pronađeni su dobro očuvani ostatci dviju srednjovjekovnih brodica. Na inicijativu voditelja istraživanja Zdenka Brusića i konzervatora Božidara Vilhara oba su plovna objekta izvađena iz mora, konzervirana i izložena u Muzeju ninske baštine, čime je projekt zadobio sustavni karakter te donedavno predstavljao jedini arheološki projekt usmjeren na sustavno istraživanje i obradu podmorskih nalaza. Unatoč stručnim i znanstvenim radovima u kojima su brodovi sumarno obrađeni, detaljna objava nalaza tek predstoji. Stoga je 2008. započeo rad na dopuni postojeće dokumentacije, a jedan od prvih koraka bio je određivanje vrsta drvene građe korištene za izradu brodskih konstrukcija. U radu se ukratko iznose rezultati dosadašnjih istraživanja i provedenih analiza, te upozorava na alarmantno loše stanje nalaza.