During descent, a diver's buoyancy tends to _____.

• A. Increase
• B. Decrease
• C. Stay the same
• D. Fluctuate

Answer: (B)

Gas volume in air spaces changes with pressure. As you descend, the surrounding water pressure increases and compresses the air in both your lungs and your buoyancy compensator. Since buoyancy from these gas spaces is tied to their volume, compressing the gas reduces the upward force they provide. The diver’s body itself doesn’t compress much, so the overall buoyant force drops as you go deeper. That’s why buoyancy tends to decrease during descent, and you’d typically adjust by adding air to the BC or managing your breathing to maintain neutral buoyancy. The other factors, like water density, change only slightly compared to the effect of gas compression.