Visual Clues During Site Assessments May Effect Shallow Water Dive Mode Choices
By: Michael S. Glenn
Sometimes dive team members may need to consider alternative techniques to conducting their site assessment and dive operation. In shallow water incidents, diving may not be the best option as cumbersome equipment, walking on soft sediment and kicking up sediment can all disturb or even bury the items being sought. In addition, using the available information and visual clues present may assist the team in selecting the best method to conduct their search.
Conducting a site assessment can be a challenging and daunting task in some situations. While all dive scenarios require attention to detail, some often get overlooked, including visual clues to bottom terrain and depth.
Water transitions or color changes, slopes in shore terrain, and waterlines all give excellent references to the depth, bottom topography and even bottom content of a specific site. Utilizing each of these can aid the team in considering the best mode of search operation from simple wading, snorkeling or actual diving. Almost every team has planned a dive operation only to find the body of water they are entering is only a few feet deep. This can be avoided with proper recognition of visual clues.
Water transitions are important visual references. Some transitions can be barely noticeable due to waves, currents and even lighting. However, in some bodies of water color conversions are marked as a visible line separating light water to dark blue water. These sudden variances generally depict dramatic changes in depth transitioning from light, shallow water, to dark, deep water. Transitions can often come in the form of clear water to murky, muddy or cloudy water. Generally, clearer or less disturbed water is found in the center of a body of water where the elements, like wind and waves, cannot shift the sediment. In addition, these areas of disturbed sediment can also be used to determine the bottom content. Red clay, fine silt, and/or organic staining can inform the dive team about the visibility they may encounter and even the rigidity of the bottom they may encounter.
Slopes in shore terrain are excellent references for divers to pay close attention to. When performing the site assessment, divers can visibly see the waves or water coming onto the shore. When the water begins to recede, divers may be able to see the angle or slope of the shore. Assessing the slope can only be performed as far as the water allows or visibility through the water will permit. Combining visual assessments of the slope with water transitions can inform the dive team about the potential angle or depth of the water. In addition, pending visibility, divers can continue to assume this slope until other transitions appear or are found.
Finally, waterlines and staining on shore features can become extremely valuable to divers when performing their assessment on dive modes. When water levels rise and fall they can leave stains and discoloration on piers, seawalls, boat ramps and even the land. Generally water movement is fairly consistent with limited exceptions due to flooding or extreme weather. However, these stains are not generally as pronounced as regular tidal changes. When performing your site assessment, dive teams should seek out visible waterlines. The presence of visible waterlines can show where the depth is lower than normal and, in some cases, can drop the water level by several feet. For in-shore dive operations in lakes and streams, the change in depth can transition the dive team from diving to snorkeling or even wading. In coastal operations changes may have limited to no effect on the mode but can change buoyancy needs or even safety concerns. Generally, shallower water in coastal waterways also increases current effects which present a completely new set of challenges.
When considering visible water transitions, slopes and waterlines, it is possible that dive teams may be able to transition away from scuba to alternate methods. In addition, recognizing potential staining from bottom content can also greatly aid in leaving potential evidence undisturbed without damaging it or even burying it in soft bottom matter. While not all dive scenarios allow for transitioning away from complete encapsulation, some shallow water incidents may allow for dive teams to employ alternate means of searching the involved areas.