Before splash standby, when a diver is unresponsive in the water, what must be considered?

• A. The dive computer reading is unreliable.
• B. The possibility of a contaminated breathing supply.
• C. Depth is too shallow for standby.
• D. The air in the surface supply is always clean.

Answer: (B)

When a diver is unresponsive in the water and a standby entry is planned, the top priority is the safety and reliability of the breathing gas. Contaminated air can cause rapid loss of consciousness or other serious reactions underwater, so you must consider the possibility that the breathing supply is not safe. Contaminants can come from surface-supplied lines, stored cylinders, or distribution components, and even small amounts can have severe effects under pressure. If you suspect or detect any contamination, switch to a known clean supply or take corrective steps before the diver enters the water.

The other factors—whether a dive computer reading is unreliable, whether depth is shallow enough to justify standby, or the assumption that surface air is always clean—don’t address the immediate, life-safety risk in this situation. Gas quality directly affects the ability to breathe safely and to perform a rescue, so it’s the correct concern to prioritize.