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Resumen: The Chiloe Inland Sea in Northern Chilean Patagonia connects the Ancud and Corcovado Gulfs through the narrow and tidally energetic Desertores Channel (DC). It therefore plays a crucial role in water exchange between northern and southern fjord systems and the sea. Despite its energetic tidal currents, the mechanisms of water exchange, stratification, and mixing in the DC have remained poorly understood. This study investigates the tidal and fortnightly evolution of hydraulic transitions and associated mixing processes in DC to understand better exchange flows in this ecologically important area of Patagonia. Using in situ observations and a three-dimensional ocean model developed in CROCO, results revealed a relatively stratified water column during neap tides and a more homogenous water column during spring tides. Model results revealed a density front in a region with shallower depths north of the DC during spring tides, characterized by abrupt isopycnal sinking and rapid velocity reduction near the surface, consistent with hydraulic-control dynamics involving an internal hydraulic jump. Model-derived composite Froude number estimates indicated a transition from supercritical to subcritical flow, supporting the hydraulic jump hypothesis. The simulated hydraulic transition converts part of the kinetic energy of the high-speed flow into potential energy associated with free-surface elevation and barotropic pressure gradients, while dissipating a significant fraction as turbulence that enhances vertical mixing. This study improves our understanding of water exchange mechanisms in deglaciated coastal settings, such as fjords, clarifying the intricate interplay between tidally induced hydraulic controls and oceanic mixing processes. It sheds light on the importance of the tidally energetic channels as conduits for water exchange, stratification, and mixing between the fjord systems and the adjacent ocean.