Courses and Distances for approaching Smith Shoal Light are given on page 59, and also under Coastwise Courses (Position No. 1). The following Courses and Distances led in a least depth of about 20 feet (6.1 m) in 1935. 1. Smith Shoal Light bearing 270° true, distant 4 mile: Direct (Northwest Channel Entrance Lighted Range ahead). Reverse (Above Lighted Range astern) 351 Passing 200 yards west of Northwest Channel Entrance Lighted Bell Buoy 1. Northwest Bar Front Light is the front range light of both the above and the following range (see Position 3). Inland Rules commence inside Northwest Channel Entrance Lighted Bell Buoy 1. 2. Northwest Channel Buoy 3 bearing 90° true distant 150 yards: Direct and Reverse_. Haul gradually to eastward, passing between Northwest Bar Front Light and Channel Lighted Buoy 5. 3. Northwest Channel Buoy 7 abeam and Direct (Northwest Channel Turn Reverse (Above Turn, Easterly, Range Passing southwest of buoys 7A and 9, 4. Northwest Channel Buoy 6 bearing 90° true and distant 225 yards; Northwest 5. Northwest Channel Inner Range Front Direct_ This section is the western end of the remarkable chain of low islands, with intervening reefs and shoals, beginning with Virginia Key, in about latitude 25°45′ N., longitude 80°09′ W., and extending in a circular sweep to the Dry Tortugas, in latitude 24°38′ N., longitude 82°55′ W. From Florida Bay westward to Dry Tortugas they separate the waters of the Straits of Florida from the Gulf of Mexico, (4) SHOALS AND CURRENTS 75 Westward of Key West there is a succession of shoals, reefs, and keys, mostly of a coral formation and very irregular in outline. The keys are low, small in extent, and, except for the Dry Tortugas, largely covered with a dense growth of mangrove. Fresh water in limited quantities is found on Marquesas Key and some rain water is caught and stored at Dry Tortugas. About 51⁄2 miles south of the main chain of keys and reefs, and extending westward from Sand Key Lighthouse for a distance of 40 miles or more, is a line of reefs, shoals, and generally broken ground which rises abruptly from the deep water of the Straits of Florida. Satan Shoal, Vestal Shoal, Coalbin Rock, Cosgrove Shoal, Marquesas Rock, and a 17-foot (5.2 m) spot 21/4 miles westward of Marquesas Rock are the most dangerous of those known at present. This line of reefs is marked by several buoys; a light marks Cosgrove Shoal and a lighted bell buoy marks the 28-foot (8.5 m) shoal, 13 miles 135° true from Rebecca Shoal Lighthouse, at the western end of the line of reefs and shoals. As a measure of safety, when standing westward of Key West and bound into the Gulf of Mexico, vessels of the deepest draft should avoid this broken ground, including the areas with depths less than 10 or 12 fathoms lying southward and westward of Rebecca Shoal and Dry Tortugas. A course which leads 1 to 2 miles south of the buoys, 12 miles south of Rebecca Shoal Lighthouse, and 8 miles south of Dry Tortugas Lighthouse on Loggerhead Key is as close as this broken ground should be approached when skirting it. The hand lead cannot be depended upon to insure clearing the dangers. The currents near the edge of the bank in this locality are variable, being influenced by the winds, by differences of barometric pressure in the Gulf and outside, and by the tides. There are strong tidal currents through the passages westward of Rebacca Shoal, a velocity of 111⁄2 knots north and south having been observed in the passage. The tidal current on and off the edge of the reef should also be taken into consideration by vessels in these waters. For about 11 miles westward of Key West Harbor there is an extensive shoal area with a number of small scattered keys on it. White sand beaches make the three southernmost keys easily distinguishable from the southward. There are several small boat channels across the above shoal ground westward of Key West. These passages are unmarked, but the dangers are readily discernible. A channel, good for a depth of 3 to 4 feet (0.9 to 1.2 m), leads westward through the reefs from Key West to Boca Grande Channel. From Northwest Channel Inner Rear Range Light, it leads to a position about five-eighth mile northeastward, and three-eighth mile north, of East Crawfish Key, three-eighth mile south of Snipe Key, and one-half mile north of Barracouta Key. Then the course is about west to the narrow channel which leads in a southwesterly direction past the northwestern end of Boca Grande Key. From near Snipe Key there is a channel good for about 4 feet (1.2 m) leading southward to West Channel, passing three-eighth mile westward of West Crawfish Key. Another channel, good for about 3 feet (0.9 m) leads southward to West Channel from a position 2 miles 57738°-36-6 west of Barracouta Key. Head a little to the eastward of Ballast Key, the small key eastward of Man Key, taking care to avoid a shoal extending three-fourths mile northward from Ballast Key. When east of the northern end of Ballast Key, pass through a narrow opening in the shoal (about 30 feet wide), heading for the key and then continue southward. Boca Grande Channel, lying about 15 miles westward of Key West, between Boca Grande Key and Marquesas Keys, affords a short cut across the shoals from the Straits of Florida to the Gulf of Mexico; but it is seldom used, as the Northwest Channel from Key West has deeper water, is better marked, and cuts off more distance for vessels coming from or bound to points northward or eastward. Boca Grande Channel is good for a depth of about 11 feet (3.4 m) and is marked by two beacons and one channel buoy. It is used only by local boats of about 6 feet or less draft. A 2° (N. % W. mag.) course will lead through the marked channel. A good anchorage for small boats drawing less than 5 feet (1.5 m) can be had three-fourths mile northeastward of Boca Grande Key. Marquesas Keys are a number of keys, roughly circular in outline, lying westward of Boca Grande Channel; they are about 4 miles long and 3 miles broad and surrounded by an extensive shoal area. A good anchorage (locally known as Mooney Harbor) for small boats drawing 4 feet (1.2 m) or less can be had inside the keys by approaching the opening between Couch Key and Round Island from a south by east direction, passing well to eastward of the coral heads at low tide 1 mile south of the opening. Other small boat harbors are reported at the eastern end and in the northwest corner of the keys. Extending in a westerly direction for a distance of 18 miles from Marquesas Keys is an extensive shoal, the western part of which is known as The Quicksands. The general width of the shoal between the 18-foot (5.5 m) curves is about 41⁄2 miles, with depths of only 2 to 6 feet (0.6 to 1.8 m) over it in spots. At the western end of The Quicksands is Halfmoon Shoal, with a least depth of 10 feet (3.0 m) on it. A red buoy, 4A, marks the location of a wreck. About 5 miles north of The Quicksands is New Ground, a narrow ridge 512 miles long in a general east and west direction, 3% mile wide, and with a least depth of 4 feet (1.2 m). Its western extremity is marked by New Ground Rocks Lighted Whistle Buoy. On the northern side of New Ground the water shoals abruptly, and vessels should keep in not less than 13 fathoms (23.8 m) to insure clearing the shoal. On the southern side of New Ground, and between it and The Quicksands, is a questionable channel, 214 miles wide, with depths of 28 to 35 feet (8.5 to 10.7 m). Spots having 19 to 22 feet (5.8 to 6.7 m) over them are found 7 miles eastward of New Ground, and the bottom inside of the 10-fathom (18.3 m) curve is generally broken. There are indications of a ridge, of which New Ground is the western end, extending eastward to Smith Shoal, and the locality should be approached with caution by all except light-draft vessels. A shoal, with 21⁄2 fathoms (4.6 m) of water over it, lies 33% miles 255° true from Smith Shoal, partly verifying the existence of the ridge mentioned. Ellis Rock, 4 miles NW. 34 W. from Marquesas Keys is marked by a beacon. Between Halfmoon Shoal and Rebecca Shoal is a channel used by steamers with local knowledge drawing as much as 18 feet (5.5 m), but it is not recommended for a stranger because of the broken nature of the bottom. Within a radius of 234 miles from the buoy on Halfmoon Shoal, and between southeast and west of it, are a number of spots, with least found depths of 20 to 22 feet (6.1 to 6.7 m), rising abruptly from depths of 6 to 7 fathoms (11 to 12.8 m). Another spot, known as Isaac Shoal, lies nearly 2 miles southeast by east from Rebecca Shoal and has a least depth of 14 feet (4.3 m). The shoals are of the nature of coral heads, rising very abruptly from the deep water surrounding them, and there are probably other shoals not found by the survey. It is also probable that there are less depths than found by the survey on the charted shoals. Currents. In the channel between Halfmoon Shoal and Rebecca Shoal slack water before the flood (northerly) occurs about 2 hours after the time of low water at Key West, and slack water before the ebb (southerly) occurs about 2 hours after the time of high water at Key West. The average velocity of the current at strength is three-fourths knots. The times of slack water and the velocity of the current are considerably influenced by the winds. Rebecca Shoal, a coral bank quite small in extent and with a least depth of 9 feet (2.7 m) over it, lies about 7 miles westward of Halfmoon Shoal. Rebecca Shoal Lighthouse (Lat. 24°34'.7; Long. 82°35'.2) is a white dwelling on a brown pile foundation on the southerly edge of the shoal. The light is group flashing white (3 flashes every 15 seconds), 66 feet (20.1 m) above the water, and visible 14 miles. A sector, in which the flashes are red, covers Isaac and Halfmoon Shoals and The Quicksands. So far as is now known the passage between Rebecca Shoal and Dry Tortugas is clear. The lower part of the passage, south of a line from Rebecca Shoal Lighthouse to Tortugas Harbor Unused Lighthouse and west of a line extending NNE. and SSW., and passing 1 mile west of Rebecca Shoal Lighthouse, has been examined with the wire drag. Included in the dragged area are the three 10-fathom (18.3 m) spots on a line about 9 miles south of the northern limit of the drag work. Until more detailed surveys have been made of the remainder of this locality, vessels of the deepest draft should use this passage with great caution, as there are probably undiscovered spots with less depths than those now charted. A vessel is reported to have struck an obstruction 2 miles 285° true (WNW. W. mag.) from Rebecca Shoal Lighthouse. No obstruction was found here with the drag set to a depth of 33 feet (10 m) or over. A vessel is also reported to have struck an obstruction with about 18 feet over it 11 miles 147° true (SE. % S. mag.) from Rebecca Shoal Lighthouse. Rebecca Shoal Channel immediately to the westward of Rebecca. Shoal Lighthouse is frequently used by vessels bound from the Straits of Florida to points on the west coast of Florida. But in accordance with the above comment relative to shoals in this area, this passage should be used with caution and vessels should continue |