When you are dealing with fresh legs you need a really large stockpot - we often use a turkey fryer setup with a big propane burner and a big turkey pot. We try to use seawater whenever possible, but if not we use heavily sea-salted fresh water. Get your water to a rolling boil, and then add the crab (halves in our case) and start timing when the water comes back to a boil -from the time of re-boil to pulling time is 20 minutes exactly. Take the crab out and immediately put it into a bucket of ice water. Let it sit for 5 minutes to firm the shell back up, and it will be ready to serve!!