## 1 Introduction
Numbers in the circles indicate observation instruments deployed or planned for deployment as follows: (1)—moored automatic mobile profiler for monitoring of the dissolved oxygen; (2)—moored automatic mobile profiler for environmental monitoring; (3)—mooring buoy for the monitoring of GNGs; (4)—shallow-water tethered profiler Winchi (presented in this study) to observe the environment; (5)—bottom mounted wave and current meter connected by an optical cable to the coast; (6)—subsurface mooring for suspended matter and carbon flux monitoring; and (7)—the terrestrial part of the observational site to observe the GHGs, carbon flux, wind, and weather. In oceanography, automated tethered profilers, known as Yo-Yo, connected by a flexible cable with bottom anchors or other underwater supports (see, for review, Reference [9]) have been used for long-term measurements of depth profiles of hydrological, biological, chemical, and optical parameters at fixed locations, e.g., in the Baltic Sea [10] and the Arctic [11]. These profilers are often equipped with several underwater sensors to assess aquatic ecosystems. Tethered profilers are usually parked at the bottom and can ascend at a speed of 0.1 m s\({}^{-1}\) and take measurements at a high-vertical resolution of 0.01-0.1 m, which is sufficient to resolve issues of fine-scale structures, e.g., thermohaline intrusions, sharp vertical gradients, boundary layers, and others. Tethered profilers may obtain data on stratification at depths shallower than 1 m, which is useful to estimate the transfer across the air-water interface and verify satellite remote sensing data. Surfacing tethered shuttle buoys, known as coastal surface piercing profilers (CSPPs), are vulnerable to sea currents and internal and surface waves. For instance, at the inshorse sites of the Ocean Observatories Initiative, CSPPs can be deployed between April and September, as the wave climate precludes deployment between October and March [12]. However, surfacing allows the profiler to transmit measurement data via radio and satellite links, which are essential for operational oceanography. Autonomous tethered profiling systems that operate in shallow waters often use winches [13]. Few winch-type profiling systems include at least two electronic control devices: one at the winch and the second one at the movable floating carrier with an environmental sensor suite, which includes a pressure sensor. Both controllers interact via a cable, because information regarding the submersion depth of the sensor carrier is crucial for the winch operation. In such cases, the underwater winch should be equipped with a waterproof slip ring or rotary joint. The disadvantages of this design are complicated maintenance and high cost. Unlike the systems that include two units connected by an underwater electrical cable, there were tethered profilers with all the modules (buoyancy, winch, battery pack, electronic control module, environmental sensor suit, and communication module) mounted on a single open chassis. A synthetic wire was wound around the profiler winch spool, and the second end of the rope was fixed to the bottom anchor. Such a profiler exhibited positive buoyancy; therefore, the winding/unwinding of the synthetic wire allowed it to descend/ascend. The most enhanced profilers of this type were custom-made underwater winches or automatic elevator system type 3 by Nichiyu Giken Kogyo Co., Ltd., Tokyo, Japan ([[https://www.nichigi.co.jp/en/en_products/en_nigkocean.html](https://www.nichigi.co.jp/en/en_products/en_nigkocean.html)]([https://www.nichigi.co.jp/en/en_products/en_nigkocean.html](https://www.nichigi.co.jp/en/en_products/en_nigkocean.html)), accessed on 22 November 2021) and Thetis by WetLabs, Inc., Philomath, USA (production discontinued). The chassis structure of the profiler was designed to mount modules of various sizes; a lot of space within the chassis remained unused owing to large dimensions of the devices, e.g., the Thetis profiler had a diameter of 0.8 m, height of 2.1 m, and weight of 100-160 kg.