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.
Since, in effect, it is free, the contractors haul it away. This practice caused massive beach erosion which reduced the Black Sea coast by 50 percent between 1920 and 1960. Eventually, hotels, hospitals, and of all things, a military sanitarium collapsed into the sea as the shoreline gave way.