Re: Which anchor
I boat on the Mississippi and I use either a coated Navy anchor (15 or 20 pound) or a slip-ring fluke anchor (sort of a modified Danforth for easier retrieval). I like the Navy anchor as an all-around anchor; it's pretty heavy and works well in a variety of substrates. If the current is swift, I'd use the fluke anchor; it really has good bite in the soft Mississippi bottom. With both I have about 15-20' of heavy chain shackled to the anchor before the rope.
If you're in calm-ish water (e.g., out of the main current), you could probably get away with a large mushroom anchor, but I mostly see those on fairly light, low profile jon boats.
Hope this helps,
Jim