Deep Sea Capsule Salvage BGM

Create an approximately 90-second underwater exploration BGM loop for a deep-sea salvage game heard from inside a small metal diving capsule. Use a slow continuous 50 to 180 Hz low-frequency current pulse as the foundation, distant industrial metal hits with long muted resonance, and a sparse blurred melodic contour around 300 to 800 Hz. The track must feel thick, enclosed, distant and patient enough for long exploration sessions. Strongly reduce frequencies around 2 kHz and above, with no bright percussion, no glassy pads, no high shimmer, no vocals, no sonar ping, no sudden cinematic impacts and no triumphant melody. Keep enough low-mid definition that the slow motif remains recognizable beneath the underwater ambience. Make the ending able to return smoothly to the opening texture for looping.