The Mycherin is available for $49.95 at buy now price on ebay. Another one to look at is the McNett Blakely varieties of dive knives. Fully serrated sheepsfoot option available, 420 SS, can be attached to vest. Available on ebay and i think also on amazon. $18-20 plus shipping.

With all due respect the fixed blade requirement is pretty much old school. Todays folding knives, the better ones, are mainly one handed open and not substantially slower to deploy or less stable or durable than your average fixed blade.

You might wish to look into the available folders and get some experience handling them and deploying them one handed. In an adaptation of good SCUBA and swimmer training, under stress if you can manage it.

A good test would be to arrange for a weighted line to be tied to your ankle and then have a friend near-drown you in the deep end of a pool. The weight makes getting air difficult but not impossible. Then your friend repeatedly shoves your head under water. Until you start to panic. Which usually happens after you get a lung full of water. At which point you are to deploy the knife, cut the line and self-rescue. This is good training for anyone who will be around water.

Of course you need a pool and a friend, or friends (even better), who are able to rescue you if you get into real trouble.

You may still decide you simply have to have a fixed blade but there are trade-offs. Fixed blade knives are fairly bulky. Additionally so because they demand a very substantial sheath with a strong retention system if your going to prevent damage to yourself, others, or vital equipment. The retention system can be as problematic when your stressed and inverted as folder. Both folder and fixed blades need a retention lanyard in case they are dropped while being used. Before being deployed a folder is much less likely to come out of its sheath and lay open a major vein while your spinning around on the bottom of a hole.

Neck knives are good in some situations but not so good in others. Unless you use a second retaining lanyard lower on the chest that holds the knife in position they wander around a lot. If your inverted they can fall completely off and be lost. After being thrashed in whitewater or falling down a hillside your as likely to find them hanging between your shoulder blades as around the front.

Fixed blade knives have some good uses in marine use. Something like this:
http://www.defender.com/product.jsp?path=-1|118|119|312085&id=78450

Is particularly good for places where you can lash the sheath in place at locations where a knife might be vital. Like the bitter-end lashings on your anchors rode, at the base of the mast and lashed onto the bindings of the life raft.

From personal experience I have found over time that even my favorite fixed blade knives are increasingly being left behind. There are precious few jobs a good folder can't do and unlike a fixed blade they don't get in my way. Like a good friend a fine folder stays out of my way until I need them.

I have a few folders that are pretty quick and easy to open, but if I am goin' down with a rock in my sock and a lung full of water, trying to find the thumbhole or little switch is just one more thing I don't want to have to worry about. I suspect (and I am not a white water kinda guy, so this is just a WAG) that a good fixed blade, in a good kydex sheath, would be what I wanted...

I've used both the Gerber River Shorty and Benchmade H20 for some years for scuba diving and they both work well and have held up.

Sog seal

The H1 will NOT rust. I promise. I swam and snorkeled with a Pacific Salt for a week in the gulf when I first got it and it doesn't show a speck of rust. I didn't do anything to protect it.

Get one of the Caspian models in your hand and see how it feels. If you don't like the grip, then the steel won't even matter.

The Gerber Shorty hasn't been around this long for no reason though. It is used by many kayakers.

That's the extent of my experience in this matter.

Jeff,

I was talking about their Salt FRN folders someone mentioned. All good,

Matt

Agreed but most of the river knives also have these little release buttons so they lock into their sheath to prevent them falling out. I am not so sure that those are any easier accessible than a folder in the type of situation you describe.

Mind you at least you know where a fixed blade is all the time and won't have to dig into your pockets like you would a folder.

"...most of the river knives also have these little release buttons so they lock into their sheath..."

Doesn't surprise me. If I were in need of such an item, in my minds eye I can see a kydex sheath (that does a good job of blade retention on its own), with a thumb break safety strap, located right where my thumb could hit it when I reached for the blade...

What about an Emerson La Griffe White Water Rescue? I've just got my daughter the standard La Griffe for MBC use and it seems rock-solid. The WWR version has a rounded tip and serrations which seems a good combination to me as I'd rather not stick the standard point into me, emergency or not .