COMMENCE TO BECOME FLAT. ThE PERIOD REMAINS UN- 

 CHANGED, BUT LENGTH AND SPEED ARE >WCREASED, THE 

 WAVE BECOMES HIGHER AND SHORTER, THE CREST ARCHES 

 FORWARD AND FINDING ITSELF UNSUPPORTED BY SUFFIC- 

 IENT WATER ON THE FRONT, DASHES DOWNWARD, PRODUC- 

 ING A WAVE BROKEN INTO SURF. 



SWELL 



As WAVES MOVE BEYOND THE WIND-SWEPT REGION THEY 

 GRADUALLY LESSEN IN HEIGHT AND GIVE RISE TO GENTLE 

 UNDULATION KNOWN AS SWELL, OR GROUND SWELL. THE 

 TERM SWELL IS ALSO USED TO DENOTE THE GRADUAL DYING 

 DOWN OF WAVES THAT THE WINDS HAD PREVIOUSLY SET UP. 



A STORM WAVE MAY BREAK AS A SPILLING BREAKER SEVERAL 

 TIMES, OR EVEN CONTINUOUSLY, AND THE CREST ANGLE 

 WILL BE ABOUT 120°. NO VERTICAL FRONT WILL APPEAR. 

 If A SWELL BREAKS ON A SHOAL, IT WILL LOSE MUCH 

 ENERGY AND NOT BREAK AGAIN AS LONG AS THE WATER DEPTH 

 REMAINS CONSTANT. THUS, ON THE INSIDE OF A SHOAL, 

 ONLY SPILLING BREAKERS WOULD BE GENERALLY EXPECTED. 



NOTE: No attempt has been made in this report 



TO DESCRIBE OCEAN WAVES CAUSED BY OTHER 

 forces OF NATURE, I.E., SUBMARINE, EARTH- 

 QUAKE, OR SUBMARINE VOLCANIC EXPLOSION. 



- 3 - 



