In retrospect, I'm very glad I didn't try impaling one of those yellowtails with my dive knife. For one thing, it's got a chisel tip, which is great for prying but not so great for stabbing yellowtails. Dive knives can function as important tools but I haven't found many occasions to use them as weapons (while diving). They are very useful for banging on your tank to alert other divers a shark is circling above them in the water.
I know hunters who carry a stiletto just for use in prying out large, wounded grouper which have wedged themselves into holes in the rocks, which is where they tend to run after being hit with a speargun shaft if they're still capable. The best thing to do is not shoot unless you can hit the fish properly in the first place. This is, of course, easier to say than it is to do.
Diving buddies come and go but I've had the same knife since I started diving. I have grown rather attached to mine and I intend to keep it until death do us part. Knives are easy to loose and it seems most divers, having lost one or more, regard theirs as transient friends. Had I lost this one in a yellowtail early on, I might have wound up harboring such a casual and pitiful attitude myself.
Sea water is extremely corrosive and my knife began rusting in spite of frequent teardowns for rigorous cleaning and thorough oilings. Most divers seem to accept such corrosion as inevitable and don't seem to think much of it. I found this rusting to be psychologically stressful and aesthetically unacceptable. I finally wound up glass bead blasting all the rusty metal parts to clean them. While I was at it I also engraved "Jennifer" in large letters on one side and the legend "Dive Buddies May Drift Away But Jennifer Sticks Forever" in smaller letters on the other.
Then I took all the metal and had a black oxide finish put on it by a plating shop. This finish served to "pre-rust" the knife and left no unprotected surfaces for sea water to work on. The black oxide finish, in conjunction with frequent cleaning and oiling during dive trips, did the trick. I now have a knife that I'm quite proud of. Cleaning my knife has become a little ritual that I take pleasure in. I have even been known to clean my knife when it didn't really need it. I still don't care much for the bright orange plastic handle although it's very possible I might have lost it once, had I not glimpsed the handle down on the bottom after beginning an ascent. I guess the handle stays.
In case you weren't paying attention when I told you, Jennifer was my first dive buddy and the only member of my certification class that didn't make it. We brought Jennifer back to Tucson laid out in a van with a couple of bags of glucose and an IV rig stuck in her arm. It wouldn't be fair to leave you with the idea Jennifer had a diving accident, although I guess she did. Her accident involved some deep diving to the bottom of several large bottles of Mexican tequila that weekend, which resulted in her collapse from acute alcohol poisoning. You really had to be there to fully understand and appreciate the engraving on my knife.