I know, I know. You’re excited. You want to lift the lid and poke them with a fork. Stop it.
Every time you lift that lid, you let out the steam. Bummer. Steam is what cooks them evenly and keeps them juicy.
How To Steam Crabs And Shrimp at Susan Burke blog
Wait until the last 5 minutes to check. Use tongs, not your fingers. You’re not a crab superhero.