re: I need some cajuns’ advice on shrimp boil.

Season the water. Get it to a boil. Put in the shrimp. Stay by the pot. Wait for the earliest signs of boiling, may take 5-8 minutes. Once you see the early signs of boiling, start checking the shrimp for a visible gap or air pocket/bubble between the shell and the meat. That usually happens 45 seconds to a minute after its obviously boiling. But keep pulling out a shrimp or three to check for that gap. Once it's there take the shrimp off the heat and toss in some bags of ice, leave the ice in the bags. Wet the sides of the pot too if you'd like. Let them soak 20 minutes or so. They will not be overcooked. The shells come off easily. I've never had a problem peeling them using this method for decades.