The key is you have to have a heavy enough anchor and enough rope out. If your trying to anchor in high wind or high current or waves from big boats...have to have that anchor out there so that the boat is not trying to bounce it and break it loose. Some anchors work better for some bottoms...but a three prong river anchor of 16lbs or so will hold pretty good when you have about two foot of chain on it then rope. Depending on conditions you may have to have out twice the amount of rope for the depth or more. Anchoring in the big rivers and in the reservoir spillways in the turbine wash we would use homemade ones a lot because we would lose them to snags. The worst thing is you will swing on the rope of a single anchor. Setting two anchors is a chore but if you want to sit still on a spot you just about have to. Hard bottoms harder to anchor on. Anchoring into soft mud deep is hard to break loose sometimes. The heavier your anchor is...and the more specific it is to the bottom type your anchoring on....the shorter the rope you can use. But the anchor needs to be pulled from the right angle to dig in right on some bottoms.
Or buy one of them new fangled gps controlled trolling motors and set it to hold you still. In shallow water though some fish won't tolerate the noise...can affect your bite.
To set still on a spot in high winds and waves you set one anchor far enough upwind of your fishin spot.....drift over the hole and downwind of the hole far enough and set the other.Pay out rope on the stern anchor as you pull your self with the bow anchor back over the spot.Then lock em both off. Some stretch in the rope helps to not break anchor out. Experience helps after a while. Using a marker buoy as a mark to put your boat helps.