Night & Limited Visibility Diving Flashcards

Which aquatic behavior is MOST commonly observed by night divers that is rarely seen during the day?

Answer: Coral spawning and invertebrate feeding activity

Many invertebrates — such as octopuses, lobsters, and corals — become active at night for feeding, making nocturnal dives rich with unique behavior.

A diver enters the water at night and cannot see the bottom. What is the safest descent method?

Answer: Descend along a reference line while equalizing frequently

Using a descent line provides orientation, rate control, and a physical reference that compensates for the lack of visual depth cues.

What condition is a night diver MOST at risk of experiencing due to the absence of natural light?

Answer: Loss of spatial orientation and vertigo

Without visual reference points, divers can lose their sense of up and down, leading to disorientation — a major night-diving hazard.

In limited visibility, a diver's torch illuminates a cloud of particles and they cannot see their buddy. What is the correct immediate action?

Answer: Stop, signal with light, and listen for buddy's bubbles

PADI's lost-buddy procedure starts with stopping, looking, and listening — using light signals and listening for exhaust bubbles to relocate the buddy.

Why is it important to allow time for night vision (dark adaptation) before a night dive?

Answer: It improves peripheral vision at the surface so hazards are spotted

Dark-adapted eyes can detect dim lights and movement at the surface, helping divers spot boat traffic, entry points, and their exit safely.

What torch-signaling method indicates 'something is wrong' or 'come here' during a night dive?

Answer: Rapid side-to-side waving

Rapidly waving the light back and forth is the universal underwater distress or attention signal used during night diving.

During a night dive briefing, the dive leader instructs divers never to shine their torch into another diver's eyes. Why?

Answer: It destroys the diver's dark adaptation and causes temporary blindness

Shining a bright light directly into a diver's eyes destroys their night adaptation and can leave them temporarily unable to see in the dark.