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Citation: K3

Document: US DIVING MANUAL REV 7

Page: 562

Section: 2B-10 U.S. Navy Diving Manual — Volume 2 PAGE LEFT BLANK INTENTIONALLY

Source confidence: 69%

Cited Passage

2C-2 U.S. Navy Diving Manual — Volume 2 Table 2C - 1. Equivalent Wind Chill Temperature Chart. 4. Underwater Visibility. Underwater visibility varies with depth and turbidity. Horizontal visibility is usually quite good in tropical waters; a diver may be able to see more than 100 feet at a depth of 180fsw. Horizontal visibility is almost always less than vertical visibility. Visibility is poorest in harbor areas because of river silt, sewage, and industrial wastes flowing into the harbor. Agitation of the bottom caused by strong currents and the passage of large ships can also affect visibility. The degree of underwater visibility influences selection of dive technique and can greatly increase the time required for a diver to complete a given task. For example, a diving team preparing for harbor operations should plan for extremely limited visibility, possibly resulting in an increase in bottom time, a longer period on station for the diving unit, and a need for additional divers on the team. 5. Depth. Risk increases with depth and planning can help mitigate the increased risk. Surface supplied diving methods and/or remotely operated vehicles (ROV) should be used whenever possible where depth poses a significant hazard. Decompression profiles at deeper depths have shorter bottom times that influence the time available for divers to work and may contribute to divers rushing through tasks on the bottom. The onset of nitrogen narcosis varies from one diver to the next and must be considered as dive profiles exceed 100fsw. Work up dives (in the water, or a chamber) to increasingly deeper depths are an

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