I will have to post the link .. can't include the pic?
http://green-manelishi.info/main/diving/images/knife&sheath.jpg
Comments on "as it was, as it is now":
One piece of steel.
No scales to trap water or make handle "too big" when using heavy mitts. I removed the scales.
One serrated cutting edge (it had two but I dulled the spine edge; it was unnecessary unless you were trying to cut into an enemy on the "backstroke").
No "line hook". A line hook is unnecessary if the primary cutting edge is sharp. If the hook is part of the primary edge it is nothing more than a reduction in usable cutting edge.
Can be used as a "hammer" if necessary.
Sheath is friction fit. No mechanism. Positive lock into sheath.
Sheath can be attached to almost any harness, etc.
Improvements that should be made:
No to chisel grind. Chisel looks cool but is not optimal.
H1 steel to reduce corrosion.
Holes where scales were bolted on are not necessary when there are no scales.
General Comments:
A knife has one purpose. To cut. Not to be pretty (although they can be things of beauty) or sit around impervious to the elements (but if they are that's certainly helpful). To cut. All else is (almost) secondary.
The sheath must retain the knife securely but not fight to retain it when it is needed by the owner. Kind of like a holster for a gun. Unless you are careless or fear being disarmed, I am unsure why a locking mechanism is needed.
Cute little knives are generally not as useful as a butt-ugly (or attractive) medium sized knife.
Cute little locking mechanisms, or better yet a spring-loaded-eject-it-partially-from-the-sheath are worse than useless.
They jam or fail.
A full tang, reasonably sized knife, needs no scales. Worse than scales are knives that are partial, half or no tang where the handle is somehow attached to the blade. A single piece of sharpened steel is all that is necessary. It's easy to clean.
My qualifications to spout off:
Do I need qualifications?
Even above water I generally carry two knives. One folds, the other does not. In the past I also carried a gun, but that's another subject.
A knife can be used for cutting many more things than lobster trap line or cave string. My education and experiences in that regard have been applied toward "what I look for in a dive knife". After all, the only
real difference is the environment in which it is being used; it's still a knife with one purpose ... to cut.