A compact submarine racing through the skeletons of enormous ancient creatures deep beneath the ocean. Giant ribs form narrow tunnels, bioluminescent fish scatter, collapsing bones crash into the path. Camera starts inches above the water. Wide reveal showing endless skeletons disappearing into darkness. Side tracking through rib cages. Frontal shot as a skull fills the frame. Final hero angle surrounded by glowing creatures. Bubbles, particles, blue fog, claustrophobic speed.