Busting Out

These things are amazing creatures but I wouldn't hesitate one second to eat one and they're at their best just after molting.

From I Fucking Love Science...

The process starts weeks before actually getting rid of the shell. Enzymes are produced and secreted in order to separate the exoskeleton. The crab also pulls and wiggles around inside the shell to encourage separation. About 24 hours before actually molting, the crab takes in a great deal of water in order to swell up and split a seam that runs along the side of the body. Once the seam has split, the crab merely crawls out. This aspect of molting takes about fifteen minutes. 

Once they have shed the old shell, their soft bodies are exposed and vulnerable, though their thin proto-shell hardens up in about a week. Depending on the age of the crab, they can go anywhere from two months to three years before having to molt again. Over the course of a lifetime, a crab will molt up to 20 times.