Which of the following symptoms indicates possible decompression sickness in others?

Staggering is a significant symptom that could indicate possible decompression sickness (DCS) in a diver. DCS occurs when nitrogen bubbles form in the body due to rapid changes in pressure, typically after a diver ascends too quickly. These bubbles can affect the nervous system, resulting in symptoms such as uncoordinated movements, including staggering or difficulty walking.

In contrast, the other choices do not reflect signs of DCS. Excessive buoyancy may suggest an equipment issue rather than an illness; clear speech indicates no immediate neurological impairment, which is contrary to the symptoms associated with DCS; and a calm demeanor doesn't typically suggest distress or the presence of symptoms. Hence, staggering stands out as a classic indicator requiring prompt attention, as it often hints at neurological involvement that can accompany decompression sickness.