"He pushed his white cup-cake cap to one side"
'Summer whites'
Public Domain'Summer whites' - Credit: U.S. Navy (Joshua J. Wahl)

Traditionally, enlisted sailors in the U.S. Navy wore white uniforms in summer ('summer whites') and navy in winter ('winter blues'). Both uniforms were worn with the distinctive white cap which Sylvia Plath refers to as the 'cup-cake' cap.

During recent years, U.S. Navy uniforms have been modified to reflect the needs of the modern service, but 'cup-cake' caps are retained as part of the 'dress uniform' worn on formal occasions.

 

'Winter blues'
Public Domain'Winter blues' - Credit: U.S.Navy (Drew Williams)