As a new branch of science in China, underwater archaeology has a great significance to the study and elaboration of the Chinese nation's marine civilization. This paper summarizes the origin, important practice and development course of underwater archaeology in China. Due to the high attention of the country, underwater archaeology has been "introduced" into China. After years of practice, laws and regulations have been continuously improved, the working mode has been continuously improved, the talent team has been continuously expanded, and the academic discipline has achieved leapfrog development. According to the current status of underwater archaeology, six development trends are proposed: the research direction changes from simple underwater archaeology to comprehensive underwater cultural heritage protection; The disciplinary construction and the academic discipline system of underwater archaeology are continuously optimized; The development and innovation of geophysical exploration and other key underwater archaeological exploration technologies are strengthened; The ability of underwater archaeological resources investigation and data acquisition is improved; Deep-sea technology and other related technical systems are transformed into deep-sea archaeological capabilities; International cooperation is strengthened.

This paper initially reviews the development of deep-sea archaeology abroad and in China respectively. The deep-sea archaeological surveys in the waters of Bei Jiao (north reef) of Xisha islands in April 2018, in the Xisha trough in August 2022 and two shipwrecks in the northwest continental slope of the South China Sea in May 2023 represent the three development stages of China's deep-sea archaeology, which are a breakthrough from zero, the discovery of sunken relics, and then the major discovery of ancient shipwrecks. The application of China's deep-sea science and technology in the field of humanities has made China one of the best in the world in deep-sea archaeology rapidly. Three suggestions are put forward: first, to complete the archaeological investigation and comprehensive assessment of shipwrecks No. 1 and No. 2 on the northwest continental slope of the South China Sea as soon as possible. It will provide important basis for the subsequent research, protection, interpretation and utilization of the wreck sites; second, based on the preliminarily formed deep-sea archaeological investigation techniques, methods and processes, planned and targeted systematic regional investigations shall be conducted in the future in the waters around the reefs with abundant underwater cultural relics discovered and the ancient important shipping route nodes; third, reference to the No. 1 and No. 2 shipwreck sites on the northwest continental slope of the South China Sea, further research and development of special technologies and equipment for deep-sea archaeology should be carried out.

With precious historical value, underwater cultural relics play an important role in safeguarding national maritime rights and interests. As the main tool for detecting underwater cultural relics, underwater archaeological vehicle is widely applied in underwater archaeological work. Based on the specifics of underwater archaeological work, typical operation process and existing work of underwater archaeology, the main characteristics of underwater archaeology work are summarized. Starting from general-purpose underwater robot, the main features of remotely operated underwater vehicle, manned submersibles and autonomous underwater vehicle and their typical applications in underwater archaeology are categorized, and the specifics of special robots for underwater archaeology in China and other countries are introduced in detail. Finally, the development trend of underwater archaeology vehicles is analysed from aspects such as operation mode, operation function and intelligence level, providing reference for the subsequent development of underwater archaeology vehicles.

This paper reviews underwater archaeological exploration technologies outside of China, including traditional marine geophysical exploration technology based on acoustic, optical and electrical methods, unmanned underwater archaeological exploration technology, deep-sea archaeological exploration technology, remote sensing exploration technology and high-precision underwater exploration technology. Additionally, it introduces seven practical cases of underwater archaeological exploration technologies abroad. Five trends in the development of underwater archaeological exploration technology abroad are put forward: first, multi-source exploration of underwater archaeology; second, the increasing significance of deep-sea research in this field; third, integration with big data and artificial intelligence technology; fourth, monitoring and virtual restoration of underwater sites; fifth, international cooperation and knowledge sharing.

The successful salvage of Changjiang Kou No. 2 shipwreck out of water is another milestone achievement of underwater archaeology in China. Marine survey technology played a vital role in raising the shipwreck out of water. This paper introduces in detail the marine survey technologies applied in the whole salvage process, including bottom topographic survey around the shipwreck, position and attitude detection, geotechnical engineering investigation, marine hydrological environment monitoring, multi-ship network navigation and positioning, steel pile position monitoring, real-time attitude monitoring, etc. A series of innovation and application of marine survey technology have provided important data for the overall salvage of Changjiang Kou No. 2 shipwreck. The efficiency of salvage operation is greatly improved, and a systematic operation mode of integrated marine survey technology in the field of underwater archaeology and wreck salvage is created.

Underwater wrecks are an integral part of marine archaeology. Multi-beam acoustic telemetry is an effective means to achieve safe and efficient detection of underwater shipwrecks. Based on the multi-angle and multi-method topography survey of the Laoniu reef shipwreck, the topography and occurrence status of the small topographic anomalous shipwreck site were obtained, which was about 10.5 m long and 3.6 m wide, and the length of the shipwreck compartment plate was about 1.8~3 m, and it was only about 10~20 cm above the seabed, these are consistent with the results of diving exploration. Through data analysis and comparison, the impact of factors such as probe distance, ship speed, and occlusion on the resolution of underwater wrecks is given. Based on theoretical principles and practical maritime investigation work, the main ways to improve the accuracy of underwater shipwrecks detection are to focus on scanning angle, to slow down speed during operation, and to design multi-directional reciprocating survey lines etc.

The detection of shallow buried objects is a difficult problem in underwater archaeology and marine survey. In this paper, the existing detection techniques of shallow buried objects under water are sorted out, and it is considered that the traditional detection techniques of buried objects under water have disadvantages, and three-dimensional synthetic aperture sonar technology is more advantageous. Through the measurement of ancient shipwrecks on the seabed, this paper believes that 3D synthetic aperture sonar can effectively obtain the information of three-dimensional structure, buried depth and high-resolution image of shallow buried objects, which can realize the detection and accurate identification of shallow buried objects more effectively.

This paper summarizes the systematic regional investigation of underwater archaeology, and probes into the method, workflow and value connotation of the regional systematic investigation in underwater archaeology through the investigation of underwater cultural heritage resources in Yushan Islands. The research points out that the core of the systematic regional investigation method of underwater archaeology is its comprehensiveness and systematicness. Its working process can be divided into six steps as follows: comprehensively and systematically combing background information-screening key underwater investigation areas-looking for doubts about underwater remains-investigation and confirmation of underwater remainsinformation collection of underwater remains-information collection of underwater remains. At present, there are still great challenges in the systematic regional survey method of underwater archaeology. In addition to the ununified survey standards and the lack of applied research, the technology of marine geophysical exploration needs to be improved. Underwater visibility, water depth and other factors also affect the efficiency of underwater exploration. It is difficult to confirm the underwater suspected target of deep burial or in complex environment. It is suggested that we should strengthen the application research of regional survey methods of underwater archaeology, actively introduce new technological means and equipment, focus on interdisciplinary cooperation and international cooperation and exchange, and constantly enrich and improve the methodological system of regional systematic investigation.

This paper introduced the working principles and application scenarios of ultra short baseline positioning system and acoustic Doppler current profiler. According to the underwater archaeological work requirements of the Shengbeiyu Island shipwreck in Zhangzhou, two types of equipment were comprehensively used to carry out real-time data collection and analysis, obtaining high-precision underwater absolute position information and accurate tidal hydrological observation data such as flow velocity direction, thereby improving the accuracy of site positioning. A real-time monitoring system for the entire site's ocean current profile was established, and an innovative underwater archaeological real-time positioning and monitoring system was developed to ensure the safety of underwater archaeological operations and provide technical support for shipwreck archaeological excavation work. By improving the anti-interference design of the ultra short baseline system, the stability and reliability of the system in the environment have been enhanced to address issues such as location jumps in work.

Navigation has a very important position in the history of marine civilization, and ships are the main carriers of navigation activities. This paper reviews 27 important shipwreck sites since the Song and Yuan dynasties, including 11 in the Song dynasty, 6 in the Yuan dynasty, 7 in the Ming dynasty and 3 in the Qing dynasty. By utilizing archaeology, a specialized discipline that studies ancient remains, to observe and study the physical remains of these shipwrecks, a preliminarily understanding of the nature of these shipwrecks, the reasons for their sinking, the wood used in ancient shipbuilding, shipbuilding craftsmanship and navigation technology is gained. It also provides important basic materials for China's ancient shipbuilding and navigation history. In addition, the maritime trade activities and merchant behavior of the time is explored by studying the goods transported on the ships. By studying the daily items of the crew or merchants retained on the ship, it can gain a glimpse of the "micro society" on the ancient ships. It also provides another perspective on the history of the development and evolution of ancient Chinese ship manufacturing, navigation activities, and overseas trade, and reproduces the living scenes of the people on board and the mobile communities.