The Aquatic Environment Flashcards
7 cards from real PADI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 The Aquatic Environment flashcards as text
Which factor most significantly reduces underwater visibility?
Answer: Suspended particles such as sediment, plankton, or debris in the water
Suspended particulates scatter and absorb light, dramatically reducing visibility; this is why disturbing sediment or diving after storms decreases underwater clarity.
What is a thermocline's practical effect on a diver descending through it?
Answer: The diver notices a sharp decrease in water temperature and possible visibility change
Crossing a thermocline produces a noticeable and sometimes dramatic drop in water temperature and may cause a shimmering visual distortion at the boundary layer.
Which ocean zone lies just below the low tide line and extends to the edge of the continental shelf?
Answer: Sublittoral (subtidal) zone
The sublittoral (subtidal) zone begins below the lowest tide mark and extends to the continental shelf edge, remaining permanently submerged and home to diverse marine life.
Why should divers avoid touching or collecting sea urchins?
Answer: Sea urchin spines can puncture skin and break off, causing pain and infection
Sea urchin spines are brittle, sharp, and can penetrate wetsuits; spines that break off under the skin are difficult to remove and may cause secondary infection.
What environmental condition is most likely to indicate a risk of strong currents at a dive site?
Answer: Tidal exchange near a narrow channel or inlet
Tidal water moving through narrow channels or inlets is funneled and accelerated, producing strong, potentially dangerous currents especially during tidal changes.
Sound travels underwater at approximately how many times faster than in air?
Answer: About 4–5 times faster
Sound travels approximately 4–5 times faster in water (about 1,500 m/s) than in air (about 340 m/s) because water is much denser and less compressible.
An atoll is best described as:
Answer: A ring-shaped coral reef enclosing a lagoon, often surrounding a sunken volcanic island
Atolls form when a volcanic island subsides and the surrounding fringing reef continues to grow upward, eventually forming a ring reef enclosing a central lagoon.