Leaving the vibrant kelp, you descend into the mysterious deep sea trenches. In this cavernous area, your primary progression goal is to locate and reactivate the buried drone robots. Swim near a buried drone and press the interaction button (Square on PS/X on Xbox) to have it dig itself out. These drones are essential, as they will follow you and use their sonar to clear the dense red coral blockages obstructing the path forward.
As you navigate the trenches, keep an eye out for three Secret Shells: one tucked behind a rock pillar near the first drone, one inside a small cavern on the left canyon wall, and a final one hidden behind a patch of sea grass near the exit. After clearing the final coral barrier, the organic environment shifts abruptly. You will transition into the mechanical pyramid structures, a series of geometric, industrial corridors. To proceed here, you must follow the blue power lines along the walls, which lead to a central doorway that triggers a high-speed current sequence into the next zone.