Unimak Pass
The Fox Islands Passes are waterways in the Fox Islands area of the U.S. state of Alaska, connecting the Bering Sea with the North Pacific Ocean .
From the southward and eastward, bound for Bering Sea, there are three passes used by deep-draft vessels, known collectively as the Fox Islands Passes, and respectively as Unimak, Akutan, and Unalga passes. The largest and most desirable one to use in thick and foggy weather is the eastern one, Unimak Pass. This is clear of hidden dangers, the widest of the three, and is comparatively free from tide rips. It is especially recommended for sailing vessels, and for steamers bound direct to the northward. Akutan and Unalga passes are convenient for steam vessels bound to Unalaska Bay, but, being narrow and having strong currents and tide rips at times, are not recommended for sailing vessels bound north. A fair wind is almost necessary for the passage, and from the southward this would bring fog. The pass between Ashmiak and Ugamok islands on the east and Sea Lion Island on the west may be clear of dangers, but it is not recommended. All of the other minor passes between Unimak and Akutan passes are known to be full of rocks and reefs. The mountains in this vicinity would be excellent landmarks if they could be seen, but in summer they are almost always obscured by fogs or low-lying clouds. The lower hills and islands and objects near the sea level furnish the available landmarks. In coming from the southward or eastward in clear weather, and if bound through Akutan or Unalga passes, it is recommended to steer for Tigalda Island as the first land to be made. It is high and prominent, and when once made a course can be shaped for any of the three passes.
Unimak Pass (54°20′01″N 164°55′14″W / 54.33361°N 164.92056°W) is the widest of the Fox Islands Passes, being 9 or 10 miles wide in its narrowest part. It is clear of hidden dangers, free from dangerous tide rips, and the tidal current has less velocity than in the other passes. Except near shore, it is free of sudden blasts of wind descending from the mountainous coast to the sea, known as williwaws. It is the most desirable pass for sailing vessels, and also for all vessels not calling at Unalaska Bay. In approaching from the southward and eastward, care must be taken to keep clear of Sannak Reefs and Anderson and Lenard rocks. If very clear, the mountains of Unimak Island may be made out and the course for Unimak Pass shaped accordingly; but under ordinary conditions the hills back of Cape Khituk, or Ugamok Island, will be the first land sighted. If the weather is thick, soundings on Davidson Bank will be of use in feeling the way in to the land. In the vicinity of Cape Khituk the coast is bold and free from outlying dangers. A reef of rocks was formerly shown on the chart extending between 1 and 2 miles from the east end of Ugamok Island. The IMO Maritime Safety Committee per IMO SN.1/Circ.331 adopted five 'Areas to Be Avoided' (ATBA) in the region of the Aleutian Island Archipelago in order to reduce the risk of a marine casualty and resulting pollution and damage to the environment. These new ATBAs will come into effect on January 1, 2016. The five ATBAs apply to vessels solely in transit through the Bering Sea and North Pacific Ocean and in most areas extends no further than 50 nautical miles from the shoreline of the islands. The 50 nautical mile buffer zone is designed to allow for the repair of, or time to launch an emergency response effort to any marine casualty before it runs aground and damages the fragile ecosystem. The establishment of the ATBA adds minimal distance to a voyage. \Akutan Pass is about 3 miles wide in its narrowest part. There are four small islets (Gull Rocks) on the western side of the pass, less than % mile from Unalga Island, with many detached rocks above water in the same group, but not extending beyond the islets into the pass. There is a reef with some pinnacle rocks on it extending from Cape Morgan not more than ^ mile into the pass. With these exceptions there are no known dangers. The current and tide rips are not so strong as in Unalga Pass. On this account, and because of its greater width and the fact that a straight course will carry through, this pass is preferred by many to Unalga Pass.
...
Wikipedia