This preprint explores how observations of the ocean surface can constrain currents and buoyancy deep below it. A score-based diffusion model generates three-dimensional interior states conditioned on surface information. The method is evaluated in an idealized double-gyre simulation with 15 vertical levels, testing both mean circulation and mesoscale variability. Its reconstructions include uncertainty estimates, with skill decreasing as observations become coarser or the target depth increases. Readers get a probabilistic approach to an underdetermined ocean-observation problem and a controlled demonstration of its potential before application to real-world observations.