Just let a bit of "air" out using the oral inflation tube(s). Much more comfortable, won't decrease buoyancy.

Ive been recently looking at life jackets and life preservers from a more sporting angle - the difference being that its function is mostly to help you swim to safety.

Ive been watching videos of the collar type preservers - the ones that go around the neck and have a large floatation bladder at the front. Seems to me that these are almost impossible to swim in, except on your back.

Is anyone aware of any lifejacket designs that dont impede your ability to swim he way the collar ones do?

The only one that comes close is the military issue LPU-10/P. I havent had any experience with this type, but it looks like it was designed with a goal of enabling you to to keep your head high and out of the water, while leaving your arms free for swimming. Has anyone had any experience with this type of device?

"You know, that was the time I was most frightened, waiting for my turn. No sir, I'll never wear a life jacket again."

Captain Quint.

You might want to look at the ones intended for canoists, water skiers.
A lot of the modern designs are intended for more freedom of movement.

Here are a couple of neoprene water ski vests from Cabela's
http://www.cabelas.com/watersports-vests.shtml
The neoprene tends to be a bit sweaty for regular wear IMHO.

Here is another store with a selection of life vests for canoe, kayak or water ski.
http://www.coloradokayak.com/Mens-Touring-Fishing-Lifejackets-PFD

The buoyancy compensators used for scuba usually are made with the tank harness as part of them but there are some available which are separate.
Because they are meant to provide adjustable flotation. They are used both as life jackets and to balance the divers weight and the weight of the air in the tank so the diver doesn't sink to the bottom or struggle to much trying to swim down they are all pretty expensive.
They would not be very comfortable for wearing all the time either because of the extra stuff on them.

You might want to look at Mustang's products too.
They started out making survival suits and have a lot of clothing that gives you flotation as well as thermal protection.
These are their life vest pages
http://www.mustangsurvival.com/products/category.php?t=3&pg=2

This is the rest of the cataloge
http://www.mustangsurvival.com/products/

The only flotation systems I've used have been Navy issue. I wore an LPU-32 the last time I qualified. The only swim stroke required or desired was the breast stroke and it is performed before you inflate. After the vest inflates you are floating, not swimming.

If you do decide to swim after you inflate the vest, partially deflate the bladders using the oral inflation tubes as DR mentioned above and swim. Inflate via the tube when it's time to float again.

The problem with swimming while wearing most life vest designs is that you're fighting a design feature of the vest, which is to turn an unconscious person face up.

So you're basically looking for something to keep the kit afloat? (Not a life jacket). As long as it is (almost) waterproof it should float... (for a while). Doesn't matter if it's heavy, because it probably is bulky as well, and as long as you're not exceeding one kilogram per liter it will float.

When canoing, I've used bags and rucksacks lined with garbage plastic bags to that effect. Clothes, tent and sleeping bag are quite bulky even when compressed. When soaked through clothes themselves will most likely stay slightly bouyant to neutral (bobbing just below the water surface), but if there are any additional heavy items (such as an axe) those items will drag your pack down. If dry, clothes will keep quite heavy things afloat. The plastic liner will keep the water out long enough for you to salvage that bag. If the plastic is new and/or robust it will be almost totally water proof (you may have some small leaks around the opening). If used for a few days you will have some punctures and some of your stuff will be wet, some of it dry and some of it somewhere in between.

So my take on this - you don't need extra flotation, just make it water proof!

If anyone has used the the LPU-10/P or knows someone who has (or can direct me to some forum where I might people who have). I'd love to hear from you.

Thank you all for your input!
The answers here are realy helpful. Then again, that is why I put the idea here.

Yeah - its true. Ability to swim requires a lower center of floatation, and an orientation different from the 30 degree backwards angled body that life jacket designs aim for.