A couple of days ago my wife and I went down 1.2 miles south of Sebastian Inlet on A1A (FL) and went screening for shells in the Indian River Lagoon there just to the west of the road. I tried a variety of spots for about 1 hour in water between 1 and 4 feet deep. The bottom consisted of grass, sand, shell rubble, and mud.
I did not get much satisfaction for my effort. I mostly collected:

Choine elevata
Nassarius vibex
Bulla Striata

I had hoped that there would be much more variety.
Matt