This paper presents the first results of both dryland and underwater investigations at the multi-period Garnys riverine site situated on the Žeimena River in eastern Lithuania. There, during 2017-2020 a professional diver and amateur archaeologist collected hundreds of Mesolithic-Neolithic archaeological finds made of wood, bone, antler, stone, and ceramic from the riverbed and on its bank. Moreover, in eroded places of the riverbed, the wooden remains of several fish weirs were observed. In 2021 professional archaeologists continued the research, including field investigations followed by various laboratory analyses. These included AMS 14C dating of 16 various ecofacts, artefacts and 46 wooden constructions, wood and animal taxa determinations, and the results of traceological analysis of the flint and osseous artefacts. Our research demonstrates that the site was intensively used for hunting, gathering and fishing during the Mesolithic and subsequent Subneolithic and Neolithic. Intriguingly, there was no evidence for agriculture, while the numerous Neolithic ceramics largely follow the Subneolithic traditions. The Garnys site is therefore unique and a clear example for delayed. Neolithisation in a forested and lacustrine area in the eastern Baltic region. During the Metal Ages, the site had been used exclusively for stationary fishing.