Eddy energy in the real ocean is often inferred from sea-surface eddy kinetic energy, but its subsurface reservoir remains poorly constrained. Using Argo-derived hydrography, we identify a pronounced mid-depth eddy available potential energy (EAPE) hotspot in the southeast Indian Ocean, where surface EKE is relatively weak but EAPE averaged over 500–1000 m is strongly enhanced and peaks near 650 m. This structure is not reproduced by three eddy-resolving ocean models, OFES, OM2, and LICOM3, revealing a systematic deficiency in representing regional subsurface mesoscale energy. Further analysis links the EAPE enhancement to cyclonic eddies generated by the Leeuwin Current–Undercurrent system. These eddies show enhanced vorticity and strong mid-depth EAPE. Removing them markedly weakens the regional EAPE maximum, suggesting that Leeuwin Undercurrent eddies sustain this hidden subsurface energy reservoir.