I fall over in 30 feet of water and you can kiss me goodbye as soon as those thngs fill with water.
That's why you always wear some type of safety belt while in waders. Could be an ordinary snug fitting nylon belt or a snug fitting neoprene ammo belt/bandolier. It will minimize your waders from filling and sinking you to the bottom. I suppose in a boat you may never need or want waders though. But in that deep of water you really should be wearing some type of floatation device too.
LOL...that's why I just don't wear waders. No need for them. Rain pants do the exact same thing for me that waders would. I was just giving an example of times when you may not need waders.