Just save you the hassle and buy an 11 or 16.5 pound sand anchor. Jerry's has the 11 pounders in stock. I think they are really called a shovel or claw anchor. Anyway, those things will stick a ship. They work on reefs and at the short rigs offshore. I believe they are around $40. Need to rig em right, though. If you get one, pm me and I'll show you how to make the anchor so that you'll never lose it. Just takes 4 foot of 3/8" chain and tie wraps. We ALL use them as guides. Mighty Mites are outdated. They won't hold offshore in 30'.
Here's a link to a picture of the anchor.
http://a1672.g.akamai.net/7/1672/116.../156780421.jpg
BD