I wear what Ed has. I bought mine for ocean passages on small sailboats and it is made so that even tropical downpours and green water across the boats cockpit won't inflate it. You have to go into the water for it to activate, you want it to inflate if the boom sweeps across the deck knocking you unconscious and overboard. It also has a manual activation. It allows very active freedom of movement and is lightweight. Got mine at Fisheries Supply in Seattle. Not cheap, but what's your life worth to you?