A colossal underwater megacity built within a massive primordial ocean trench, towering kelp纤维素 spires reaching toward the surface with integrated solar collector membranes, suspended biodome districts glowing with bioluminescent algae, sleek dolphin-shaped craft gliding between coral archways, sky gardens with floating photon-producing plankton, deep ocean teal and electric cyan palette with soft sun rays filtering from above, epic upward shot from central plaza with tiny silhouetted marine biologists on illuminated observation platforms emphasizes impossible oceanic engineering scale, photorealistic, cinematic depth of field