So as it's only about 16 foot of water I try leaning over the side of the dinghy with a facemask on (kept on board for just such occasions..). Unfortunately the visibility is about 8 feet. Next, dive down in my underwear (not having packed any swimsuit) to have a look. The anchor is firmly wedged in some metal junk. The eye for the trip-line is buried somewhat in the ooze and I can't get to it, but I tie a line to the shank as far down as I can get. Back up to the surface, let out the chain and make fast the line. Try heaving on it with the foredeck windlass. Nope. Let more out and try backing up with the engine to pull on the line. Still no good.
It just so happens that I had bought some scuba gear at a sale earlier in the year, which I hadn't tried out. Should be interesting if nothing else, I think. So I call home on the cellphone and get someone to bring it out to me, then row ashore to collect it. Still no swimsuit, but I've got a wetsuit. Misplaced my best facemask, but still got the boat one that leaks a bit. No big deal to clear it every few minutes with an air tank, though. Next problem, the zip's a bit corroded on the wetsuit (why they use aluminum instead of glass filled nylon or epoxy graphite I don't know). A bit of work with sandpaper and that's fixed. Assemble the gear, hoist the "rigid replica of code flag A" that's sure to baffle 90% of boaters, and off we go. Contrive to dig down to the eye in the head of the anchor and secure the line. I can't budge the anchor myself. Back up, and try pulling on the line again with the engine. Nothing. Next, set a kedge anchor in case the main one actually comes free. Back down with the scuba gear, to find that the anchor has actually come free but that the chain appears to be looped up on something. Follow the chain, trying to gather it up and adjusting buoyancy so I can lift it without stirring up so much mud I can't see. Doesn't appear to be caught anymore. Back to the surface, divest myself of scuba stuff, haul in main anchor, untangle lines, etc. Then retrieve kedge against a certain amount of wind & current, using the jib sheet winch. Finally clean up mud deposited by kedge on cockpit seat and stow all lines. Then return home in triumph breathing noxious fumes from leaking exhaust system (but that's another story...).