Shrimp that hatched in the Marshland will move out to the open Gulf when they are large enough to make it in the wild.
Day time they bury themselves in the bottom. At night they come up near the surface to feed. The nights when
the Moon is right a strong outgoing tide develops, the larger shrimp will follow the tide just a few feet under the
surface and work their way to the Gulf of Mexico.
Shrimpers drop nets several feet down into the out going moving tidal water; the shrimp then move into the net.(by accident)
That is just one way of catching wild shrimp.