## 1 Introduction  
In 2009, the Ocean Observation Initiative (OOI) observation network program launched by the National Science Foundation of the United States mentioned two real-time submerged communication methods [1]. One transmission method is through submarine cables, which is suitable for near-shore observations [2]. The other operates through the acoustic transmission of an underwater glider, in which the submerged buoy data are transmitted to a glider through an underwater acoustic modglider floats to the sea surface, the data are transmitted through satellite communication [4], which is suitable for densely distributed submarine buoy arrays. As such, the submerged buoy needs to be equipped with an acoustic modem, which not only consumes a lot of power but also transmits a limited amount of data at a time. This problem makes it difficult to achieve long-term real-time data monitoring.  
In addition, the SeaCycler elevating submerged system developed by ODIM Brooke Ocean uses an underwater winch to control the rise and descent movement of the floating communication buoy [5] and periodically releases the float to the water surface for data transmission. Once the transmission is complete, the underwater winch drives the floating buoy below the sea surface. At the same time, WET Labs in the United States and NGK OCEAN in Japan have also developed similar underwater winch platforms [6]. To perform the real-time transmission of underwater monitoring data, the winch installed on the main float is used to control the rise of the floating communication buoy to the sea surface to transmit the underwater observation data to the shore station through satellite communication [7]. The above methods of using underwater winches to achieve real-time communication between submerged targets have the problems of the large volume and complex structures of underwater equipment, which lead to the low reliability of the winch and difficulty of deploying winches at sea.  
In addition, the Ocean University of China developed a Timed Communication Buoy System (TCBS) in 2015 [8]. The main underwater float is equipped with multiple ejection-disposable autonomous communication floats (ACFs). The main control of the floating body releases the ACFs to the sea surface for satellite communication according to a set timing. Since it can only be equipped with four ACFs, it usually takes at least dozens of days to release one of them, and hence the data timeliness and long-term in-place ability are poor [9].  
In summary, although several real-time communication systems have realized real-time data monitoring, there are still major deficiencies. Underwater gliders are equipped with acoustic relay transmission, which is limited by power and is only suitable for short-term communication. Due to the complex structure of underwater winches, the long-term stability is low, the cost is high, and the deployment process is complex. The number of communication floats that can be carried by the Timed Communication Buoy System is limited, and the timeliness of the data is low. In this paper, we designed a real-time communication subsurface mooring system to solve these deficiencies, which refer to the previous research on satellite communications. Compared with previous studies, this system has the characteristics of strong real-time data transmission, high success rate of data acquisition, and long-term continuous on-position operation.