If those sounds are from the sub, the hull is still intact. Assuming that, I think it would be possible for the sub to not be resting on the bottom. That doesn't necessarily mean that it's at a stable depth. It could be sinking slowly until it reaches a depth where it's neutrally buoyant, or the bottom. It could have already reached that neutrally buoyant depth, which could be the surface, or close to it. In any case, it would certainly be drifting.