This article describes early development of the climbing perch Anabas testudineus in relation to its buoyancy dynamics. Main patterns of the ontogeny during the first 140 h of development are described. The climbing perch is characterized by positive buoyancy of eggs and early larvae not usually found in other freshwater fish. This allows the fish development close to the surface of the water and is enabled by a large oil globule in the yolk. The data on the spatial orientation of the larva body, their vertical distribution in the water column, the beginning of exogenous feeding and locomotion, and the fright reaction of the larvae at different ages are presented. The most significant changes in the behavior of the climbing perch larvae are associated with changing the shape of the yolk sac, beginning to function as a provisional hydrostatic organ from about the 80s hour of development.