-- Last Updated: Apr-04-10 8:40 PM EST --
Yes, you can drown in a pfd.
You are more likely to drown while wearing a pfd, "IF" you are a "non" swimmer.
If you "were" able to swim, you might be able to avoid some of the nasty spots you don't want to go with, or without a pfd.
Examples: Being swept into a strainer; downed trees in the river, or hanging over & into the river. Most of these can be avoided, even if you are in the water; if you have some swimming skills, and are able to swim aggressively to a safe area.
Being swept into an area of the river where there is a hydraulic. Some places in the area where I live have low water bridges; some of them have hydraulics on the downstream side. Some of them have large culverts running underneath the low water bridge; those culverts are "often" jammed at some point with fencing, tree limbs, fence posts, trash cans, fishing line & other obstructions.
Not a fun spot to get swept into due to the lack of ability to aggressively swim to a safe area, before you get swept into the hydraulic, or the culvert.
Foot entrapment can sometimes lead to a drowning whether you have a pfd or not. Often the current will be too fast for you to keep your head above water when your body is swept downstream(your foot stays entrapped), even wearing a pfd.
One of the first things a lot of beginners/non swimmers do when they capsize in fast moving water is to stand up; this is an ideal situation for a foot entrapment. Will your non swimming friends be able to get to where you are, and stabilize you long enough to get whatever is entrapped free?
Some rivers, have boulders that have undercuts, and potholes. A pfd is no gurantee of safe passage or easy exit if you get swept under an undercut boulder, or into a pothole in a boulder garden. With swimming skills, you may be to avoid these hazards by swimming aggressively to an area of safey before you encounter those hazards.
Most pfd that paddlers wear are "not" designed to keep your face out of the water if you get knocked out, or stunned.
Pfds are no gurantee that you will not be affected by hypothermia, and possibly drown. Swimming skills and a pfd might have gotten you out of the water & to shore "before" hypothermia occurred.
You are a swimmer, and are wearing a pfd. You capsize your canoe/kayak. A foot gets entangled in some gear, rope, whatever. The pfd will not guarantee that you will not be tacoed between the boat & a rock, tree, or root wad. A pfd will not guarantee you will not be swept over a water fall while attached to the kayak/canoe. Many waterfalls have hydraulics & strainers at the bottom.Think swimming skills might be handy if you can get loose from your boat? Is your pfd wearing, "non" swimming paddling partner going to swim out to where you are & assist you in getting free before you drown?
A pfd is no gurantee that you will not be drowned by someone you attempt to assist, if they are extremely panicky & aggressively trying to keep their head above water(perhaps because they "don't" have on a pfd, or can't swim). If you have a pfd on, and have some swimming skills you might be able to stay away out of their reach, and assist them "after" they calm down. Or you might be able to do a reaching assist in deep water; keeping a respectable distance from the panicked non swimmer. You should be wearing a pfd to do this; and if you are going into deep water you should be a swimmer too.
I have seen a large Labrador Retreiver nearly drown a young child wearing a pfd, in 4 feet of water. The child could not get the dog off of her & the dog was holding her underwater by putting it's front paws on her shoulders. A parent had to pull the dog off the child.
That's just a few examples of how you can drown with a pfd on.......but have no swimming skills.
Swimming skills assist you by allowing you to get to shore & out of harm's way, "before" you get into some of the scenario's described above.
You won't drown because you always paddle on slow moving rivers, close to shore, the weather is great, and you always wear your pfd?
More drownings occur in that type of scenario/venue than occur on whitewater. That's because most beginners, most non pfd wearing paddlers, most non swimming paddlers go paddling/floating........on what they think are the "safe" rivers.
Again, those are "just a few" examples.