The sun never actually descends into a lake. Yet its reflection appears on the water's surface, clear and vivid. In much the same way, Krishna — unborn, imperishable, the sovereign of all beings — appears in the world without ever losing His transcendent nature. He takes shelter in His own prakriti and manifests through His own maya.
This is the heart of the avatar doctrine. Krishna's appearance on earth is not a compulsion. He is not pushed into birth by karma the way ordinary beings are. His manifestation is an act of will, of divine choice. Maya does not control Him — He wields it.
The distinction matters. When we are born, we forget who we are. When Krishna appears, He remains fully aware, fully sovereign. His birth is a gift to the world, not a consequence of past actions.