I don’t know about being the god of the this thread, but thanks for the designation all the same 
I’m on my way out of town for the weekend, but I’ll re-post a couple of experiences I shared this summer in another thread.
–I saw a moray eel strike out from a crevice and nail a grunt. Boy, you should have seen the sand fly! I don’t know who was more surprised, me or the grunt.
–I’ve had reef sharks and barracuda around me, but that’s no big deal for anyone who frequents reef areas. I once had a spotted eagle ray come right up to me at eye level; usually one only gets to see rays from above. I’ve actually fed stingrays.
–My encounters with angelfish are legion. They were intent on eating my sponge specimens right through the mesh of my ditty bag. Tenacious buggers.
–One summer, I was on the RV Seward Johnson (the same vessel featured in the current Smithsonian feature “Galapagos 3-D”) in the Bahamas. A colleague and friend of mine (Brian) and I took one of the Zodiacs out to a reef about 1/2 mile off the shore of a small, uninhabited island. The reef was shallow enough that we just had snorkel gear.
Anyway, we anchored out by the reef, we made our collections, and then I decided to snorkel over to the island while Brian continued exploring the reef.
Well, about halfway to the island, I came across the largest barracuda I’ve ever seen. Now, I’ve been around barracuda and never felt threatened. They are usually not aggressive (unless they want your spearfishing catch). However, this one probably had not seen too many humans, if any. It was obviously used to being “king of the grassbed” where I encountered him.
This huge fish (which is basically a tube with teeth–lots of teeth) decided it wanted me out of the area. It rushed at me with mouth open, peeled off at the last second, circled, and continued to repeat this pattern.
“Okay, don’t panic; don’t panic; don’t panic; just make it to shore, you can do it; don’t panic. Okay fish, I don’t want to be here–I get your point. Oh God, please don’t let me die like this out here. Okay, they say barracuda are attracted to shiny objects; okay, fish, I’m swimming with my arm (with shiny gold bracelet) out of the water–nothing to see here, nothing to see here…”
I was terrified, no other way to put it. I could see everything very well through the mask, and I honestly thought I was going to die. This big guy kept rushing me with mouth open. I had visions of a medivac situation with chopper, legs missing, or me bleeding to death before even getting back to the ship. (To top it off, I was “skinny-snorkling”–bare-assed naked except for the snorkel gear. I also had horrible thoughts of what the newspaper account would say.) I was about 1/4 mile from shore and 1/4 mile from the Zodiac.
I eventually got the attention of Brian when he popped up for a breath. I was yelling at him to “get your ass over here, now!!!” He brought the boat around, and I swear I don’t even remember getting from the water into the boat, it was that quick.
But don’t let that put anyone off diving. 
Oh, and thanks for the link jk1245. I skimmed it, and will pay it closer attention when I get back. Looks very interesting.