SYZYGY 



sway — See ship motion. 



swell — 1. Ocean waves which have traveled out 

 of their generating area. Swell characteristi- 

 cally exhibits a more regular and longer period 

 and has flatter crests than waves within their 

 fetch. (5) 

 2. See rise. 



swept area — An area determined to be clear of 

 navigational danger. 



swim bladder — See air bladder. 



swimmer's itch — See schistosome dermatitis. 



symbiosis — A relationsliip between two species in 

 whicli one or both species are benefitted and 

 neither is harmed. Some authorities restrict 

 the meaning of symbiosis to those interrelation- 

 ships between certain plants and animals. See 

 commensalism, mutualism, inquilinism. 



synchronous resonant wave — One wave whose 



period is equal to the natural period of the water 

 basin, or the period of roll of a ship. 



syncline — A told or arch of rock in which the 

 strata dip inward toward the plane of the axis. 

 See anticline. 



synoptic chart — Any chart or map on which data 

 and analyses are presented that describe the 

 state of the marine environment over an area 

 at a given moment in time. 



synoptic oceanography — The study of the physi- 

 cal spatial field of parameters tlirough analysis 

 of simultaneous observations from many plat- 

 forms. The regular repetition of a pattern of 

 simultaneous observations. 



syzygy — The two points in the moon's orbit when 

 the moon is in conjunction or opposition to the 

 sun relative to the earth; time o.f new or full 

 moon in the cycle of phases. {See figure for 

 tide cycle.) 



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