BLACKWATER BLOCK

Blackwater is essentially fresh water with high levels of tannins. When fresh bodies of water are located in heavily forested areas, tree branches, leaves and other nutrient heavy, earthy, green waste ends up in the water and gathering at the bottom. Tannins are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term tannin is widely applied to any large polyphenolic compound containing sufficient hydroxyls and other suitable groups to form strong compounds with various macromolecules. The term tannin refers to the abundance of these compounds in oak bark, which was used in tanning animal hides into leather. The tannin compounds are widely distributed in many species of plants, where they play a role in protection from predation and might help in regulating plant growth. The astringency from the tannins is what causes the dry and puckery feeling in the mouth following the consumption of unripened fruit, red wine or tea.

All these nutrients and tannins turns blackwater to literally that, black, it looks bronze/brown/dark gold depending on how much light is allowed to penetrate but very quickly absorbs any ambient and/or surface light. In some situations the visibility can go from low to absolute pitch black in a matter of 6m/20ft. This job is a great example of a low success probability search. The location of the lost item(a phone in this case) was not known within 300m radius, and at that was still only a visual estimation, nearly a week after the phone was lost. After descent from the surface the visibility quickly dropped to zero, even using an underwater torch (dive light) could not overcome the darkness and the beam was more distracting before being absorbed by the black. The max depth to the Botton was 40ft/12m+ and after 15ft/5m the light already disappeared. In addition to the obvious difficulties of not being able to search more than a 6’’ x 6’’ area at a time, the hazard of built up debris on the bottom including branches and entanglement dangers are at their peak. The maximum effort was made for over an hour to make attempts at finding the area and finding the bottom but the reality of searching an area the size of a football field, 6’’ at a time 12m/40ft underwater for a cellphone was a losing battle. After exhausting efforts the decision was made to call the search.