Crabs and shrimp are a staple food source for fish like the Redfish, black drum, pompano, and other popular saltwater sport fish. These are fun fish to catch while fishing flats as you can sight cast to them while they are eating. I fish a lot for redfish down in the Gulf of Texas and the reds down there love eating crabs. Most crabs are difficult to tie, but when you get them down they can work really really well.
This crab fly has worked really well for me and my closest fishing buddies for fishing redfish in the Gulf of Mexico. It is a great representation of a blue crab, but can mimic other crab species if you want to tie it in other colors. It sits on the bottom in a defensive stance which make it look like a crab trying to use its pinchers against a redfish or other crustacean eater. They aren't easy to tie and definitely aren't quick, but do work well. So give it a try.