if you keep them heavily iced down before cooking, they essentially are comatose from the cold, and don't struggle like that when you put them in the water.
When we had a hundred or so to cook at Catalina, when the pots were full we put them on the floor and had lobster races while they were waiting for their turn!
Just curl their tail up and stick their heads in the water and it only takes about 3 seconds before they lose their kick.