I get them at the Pier or you can go to southshore at low tide and throw a crab pot in. Just south of birdlings at bayleys aerials but you get rig all along that coast line. For crabs size doesn’t matter just cut them in half or into quarters if it’s a big crab, hook it up and wrap bait cotton around the legs to keep it on, with really small crabs you can use them whole. Without tying them on with bait cotton you’re wasting your time, it’ll probably come off when you cast.
Crab works best because it’s their main diet around these areas, but any type of crustaceans will work for bait (crabs, crayfish, shrimp, prawns etc).