they inflate with manual or automatic triggers, the most flotation of one i've seen has been 40 pounds, if you go in with a coat, waders, clothing under waders, and boots 40 pounds isn't going to matter much. even with waders alone it will not help, or much at all. sadly the only way to save your ass is to use it and cut the waders off, don't worry about your leg. cut with the grain not against it. float coats are bulky and not for hiking but they will pull up an anchor, thee is foam in the back chest and sleeves so i think they are the best. and they are very warm!