It depends which NCIS you are referring to. CBS broadcasts NCIS, NCIS: Los Angeles, and NCIS: New Orleans. NCIS is aired on Tuesdays 8/7c. NCIS: Los Angeles is aired on Mondays 10/9 c. NCIS: New Orleans is aired on Tuesdays 9/8c.
Whereas groins are built to change the effects of beach erosion, jetties are built so that a channel to the ocean will stay open for navigation purposes. They are also built to prevent rivermouths and streams from meandering naturally.
Beaches are constantly moving, building up here and eroding there, in response to waves, winds, storms and relative sea level rise. Yet when commoners like you and me, and celebs like Steven Spielberg, build along the beach in places like Southampton, N. Y., we don't always consider erosion.