7863 HYDROGRAPHIC MANUAL PaGE 744 



7863. Marine Vegetation 



The limits of grass and other marine vegetation extending near the surface must 

 be indicated. Wherever a distinctive symbol has been adopted for such vegetation it 

 should be used, except that limits only of extensive beds should be outlined by symbol, 

 the character of the vegetation within being indicated by appropriate legend. 



The symbol for grass or any other land vegetation should not be used to represent 

 marine growth. If the bottom is grassy, the standard bottom characteristic abbre- 

 viation for grass should be used. 



7864. Kelp 



Kelp is one of the most important of the seaweeds encountered on a hydrographic 

 survey and should be indicated on the smooth sheet wherever located. One of its 

 principal characteristics is that it generally gi'ows in rocky bottom and for that reason 

 its presence indicates a possible danger. This is particularly true in Alaska where the 

 only indication of many submerged pinnacle rocks may be a strand or two of kelp. In 

 exposed waters kelp may grow in depths of 9 or 10 fathoms and in protected waters it 

 may grow in even greater depths. Dead detached kelp should not be confused with 

 live kelp attached to rocks; the former floats on the water in masses, while the latter 

 streams away level with the surface. (See also 36236.) 



Kelp should be shown by symbol where the patch is a small one. Only the limits 

 of extensive beds need be delineated by symbol, the remainder being indicated by 

 appropriate legend. Where the kelp is towed under at certain stages of the tide such 

 information should be added to the smooth sheet. 



7865. Tide and Current Stations 



The locations of all tide and current stations shall be shown on the smooth sheet 

 by blue circles, slightly larger than a hydrographic station symbol, accompanied by the 

 name "Tide Station'' or "Current Station" lettered in blue. 



7866. Wire-Drag Finds and Clearance Depths 



Where a contemporary wire-drag survey has been made, all drag finds, including the 

 bottom characteristics, should be transferred to the hydrogi-aphic sheet in green ink and 

 in the same depth unit as the soundings. Where a wire-drag examination has been 

 made to determine the least depth on a shoal or obstruction, the least depth found (if 

 less than that of the hydrographic survey) should be plotted in pencil, and a note with 

 a leader added giving the least depth with position number and day letter, and the 

 clearance depth obtained. 



7867. Ferry Routes 



Each ferry route should be shown by a single dash line representing the actual 

 route as nearly as it can be determined without sextant angles. Each terminus should 

 be marked "ferry." 



7868. Wrecks 



Within the area of the survey, wreckage not afloat is located and should be shown on 

 the smooth sheet in accordance with the symbols shown in part "O" of the Symbols and 

 Abbreviations chart (fig. 189, part IX). Wrecks are of two kinds, stranded and 



