Tidepool Tim says, "Green crabs are invasive to the Gulf of Maine, and they are now quite widespread. We find these hiding underneath large, flat rocks in rocky intertidal areas.  We might flip one rock and see 2 or 3 large crabs. When you pick one up, approach it from behind with your hand and pinch its "shoulders" in and forward to brace his claws away from your fingers. The big ones have a strong pinch. Or find a small soft shell to pick up and you won't have to worry."