This paper deals with the specifics and methods of revealing and documenting rock art at the flooded and deteriorating site of Ust-Tuba III on Mount Tepsey, on the right bank of the Tuba River at its confluence with the Yenisei. Petroglyphs from that site have been known since the mid-19th century, and their most comprehensive surveys were undertaken by Alexander Adrianov in 1904 and Yakov Sher in the 1960s, before their flooding by the reservoir of the Krasnoyarsk Hydroelectric Power Station. Sher had copied and published 98 decorated surfaces. The most numerous among the chronologically heterogeneous images are those of the so-called earliest stratum. The site is highly important for understanding the rock art of the Minusinsk Basin in general. At present, a more accurate recording of imagery is required for reliable interpretation. This is achievable by using more advanced documenting techniques and by the fact that the site is still available for study during periods when the water level in the reservoir is lowered. By 2023, about a half of the surfaces copied in the 1960s had been preserved. During their search and redocumenting, 34 new ones have been revealed. Most are situated above the water level, and some are at high altitude on rocks that are hard to access. Problems involved in the recording of such objects are addressed, and search strategies are described. Photographs of some newly detected panels and tracings of images on them are published. New findings have extended the database on the Minusinsk rock art and especially on its important and complex constituent— the earliest stratum, which has yet to be attributed both culturally and chronologically.