Avoid Problems Associated With Diving in Poor Visibility and in Very Clear Water

 

 

 

 

 

 

 

 

 

 

 

Avoid Problems Associated With Diving in Poor Visibility and in Very Clear Water

Severe reduction in underwater visibility presents challenges when scuba diving. Poor visibility makes communication using hand signals more difficult, makes navigation by visual references tricky, and can cause disorientation as to depth and direction. However, many divers do not realize that diving in very clear water can also present difficulties. In very clear water, other divers appear deceptively near (water's magnifying effects make objects appear nearer and larger), leading divers to inadvertently stray too far from their buddies. Many divers also find that gauging depth and distance in very clear water is challenging. In some cases, divers have reported the sensation of vertigo when looking down through very clear water. Here is my advice on how to avoid problems associated with diving in both clear and turbid water.

Considerations for Diving in Reduced Visibility:

Diving in reduced visibility can be disorienting for divers who are not prepared for it. However, with proper precautions and techniques, diving in poor visibility can still be enjoyable! Reduced visibility challenges divers to hone their navigational and referencing techniques, and allows them to experience a greater variety of dive environments than divers who shy away from situations with poor visibility. Here are techniques for making diving in reduced visibility easier.

 

1. Referencing:

Learning to use a variety of references to maintain orientation greatly increases a diver's sense of control and enjoyment in poor visibility. The most obvious references are a diver's gauges, including his depth gauge and his compass. A diver should be sure to check his gauges frequently during a dive in reduced visibility to maintain awareness of his depth and direction.

Other methods of referencing exist. For example, a diver who becomes confused as to which direction is up may observe his exhaled bubbles to reorient himself, because bubbles float upwards. A diver's ears provide information about his depth. If a diver is attempting to maintain a constant depth but feels the need to equalize his ears, he can be sure that he has inadvertently descended. Similarly, a diver who feels the need to equalize his ears more quickly than usual during his descent will know that he has exceeded his normal descent rate.

Finally, many divers find descent and ascent lines useful. These are sturdy ropes attached to a point on the surface (such as a buoy) and a point on the bottom. Not only do these lines provide a physical reference (a diver can grab the line to stabilize himself), a diver who uses a descent/ascent line will be sure that he descends and surfaces in the expected location. During shore dives, the natural contour of the floor may be used to maintain orientation in a similar manner.

2. Communication:

In very poor visibility, a diver may find it difficult to see his buddy's hand signals, or even to find his buddy! A diver in reduced visibility must take extra care to remain close enough to his buddy to effectively communicate problems in an emergency. Special training is helpful (and in some cases required) to dive in areas where extremely poor visibility is likely. As an example, cave divers, who face the possibility of zero visibility due to light failures or silt-outs, learn to communicate and respond to emergencies by touch. In areas where a halocline is responsible for poor visibility, divers may use light signals to communicate.

3. Navigation:

If the visibility underwater is poor, navigation by visual references becomes difficult and divers must rely on other clues to successfully explore a dive site. The ability to navigate using a compass becomes important in low visibility, which is why this skill is taught during open water certification. However, compasses are not the only way to navigate in poor visibility. During wreck and cave diving courses, divers learn to navigate by using a guideline, which they place to mark their return route to the open water. Learning to effectively and safely deploy a guideline takes practice and special techniques, do not attempt to deploy a guideline without training.

 

Considerations for Diving in Clear Water:

Surprisingly, clear water can also be disorienting. Underwater, objects appear about one third closer and larger than they really are due to the magnifying properties of water. This creates some issues when diving in exceptionally clear water. Here are some points to consider:

 1. Buddy Distance:

One concern when diving in very clear water is that divers tend to think that their buddies are closer than they are, leading divers to stray dangerously far apart. In general, a diver should be close enough to his buddy to be able to call his attention and access his alternate air source regulator in a matter of seconds.

 2. Depth Judgement:

In very clear water, the bottom may appear much closer than it actually is. Divers have been known to misjudge the depth of the bottom (or the distance to the surface) and descend deeper than originally intended. A diver should be sure to carefully monitor his depth gauge to avoid exceeding his planned maximum depth in clear water. He can also use references such as the pressure in his ears to notice if he is descending too far or too quickly.

 3. Vertigo:

Some divers can experience the sensation of vertigo when looking down through very clear water. The best way for a diver to control the sensation of vertigo is to use a visual or physical reference point to orient himself during ascent and descent, such as an ascent/descent line or the natural floor (in the case of shore dive). In the worst case scenario, a diver experiencing extreme dizziness can grab the line or touch the floor to steady himself. If the sensation of vertigo does not pass after a few moments, end the dive.

 

The Take-Home Message About Diving in Exceptionally Clear or Turbid Water:

Both clear and turbid water can cause divers to become disoriented. Determine the expected visibility before a dive and adjust the dive plan accordingly. If the visibility ever causes a diver to feel uncomfortable, impedes a diver's ability to control his depth or position in the water, or makes communication between buddies difficult, it is time to end the dive.