More good advice from the U.S. Coast Guard Auxiliary:
There are two reasons to anchor: 1.) to attach a boat to the bottom and 2.) to keep a boat in position when there is an emergency.
What anchor is best? That depends on the boat, the kind of anchoring needed and bottom conditions. While a variety of anchors are available including include plow, grapnel, mushroom, box and Danforth, the techniques that follow generally apply to all.
Marine chandlers should have a chart recommending the size of the anchor relative to boat size. It’s a good idea to attach 6 to 12 feet of chain between the anchor and the anchor line.) This adds additional weight to the anchor and making hooking a bit easier and reduces the probability of dragging.
The useable length of the anchor line (rode) should be at least 10 times the depth of the water. The amount of line paid out, the ‘scope’ should be at least 7 times the depth of water. If using a box anchor, the scope needs only to be twice the depth of water.
When anchoring, determine the water depth. Make sure that when the boat swings around due to wind or current, the boat will not hit another boat, go aground, or hit something else. Head into the wind. Come to a complete stop and slowly lower the anchor by paying out the line hand over hand. Do not throw it!
Once the anchor is on the bottom, slowly back the boat until there is about 3 times as much line out as the depth. Holding the rode over a cleat one should be able to feel the anchor as it drags over the bottom. When it “sets” firmly, the boat will stop. After the anchor is set, let out more rode to get the needed scope. Make sure the anchor line is tied off to a cleat.
It is a good idea to look at several land objects, like special trees, rocks or buoys. If these objects stay in their relative position to the boat, the boat is not dragging. If they change significantly, the anchor may need to be reset.
The United States Coast Guard Auxiliary is the uniformed volunteer Component of the United States Coast Guard created by an Act of Congress in 1939. The Auxiliary, America’s Volunteer Guardians, supports the Coast Guard in nearly all of the service’s missions.