A ship at anchor is not held by the weight of its anchor alone. A vessel that weighs thousands of tons could never be stopped by a lump of metal a fraction of that mass. What actually keeps the ship in place is a combination of friction, geometry, and the drag of a chain lying flat along the seabed. The anchor is only one part of a system, and understanding how that system behaves explains why a ship can ride out wind and current without drifting.
How Anchors Grip
The key to holding a ship is horizontal pull, not vertical weight. When a ship pays out its anchor, it also pays out a long length of chain, called the rode or scope. The point of that length is to make the pull on the anchor as close to horizontal as possible. If the chain rose straight up from the seabed, it would simply lift the anchor off the bottom. Laid out long and low, it drags the anchor along the sediment until the flukes bite in.
Once a fluke digs into sand or mud, the seabed itself does the work. The buried anchor resists being dragged because the sediment ahead of it has to be sheared or pushed aside, and that resistance grows with depth. A well-set anchor can hold many times its own weight because the ground it is buried in supplies most of the force.
Parts That Matter
Every part of the ground tackle plays a role, and a failure in any one of them can let a ship drift. The flukes are the pointed blades that dig into the bottom; the shank is the long arm that transfers pull to them; and the crown and stock help the anchor land in a position where the flukes will turn downward rather than skate across the surface. The chain adds weight low in the water, which keeps the angle of pull shallow, and it also absorbs shock as the ship surges on waves.
Different anchor styles pair those parts in different ways, and short explainer videos on channels devoted to Anchors; often show the moment a fluke rotates and buries itself, which is easier to grasp in motion than in a diagram. Watching the geometry work makes it clear why the shackle, the swivel that stops the chain from twisting, and the shank angle all matter as much as the flukes that get the attention.
The connection between chain and anchor, usually a heavy shackle, is a common weak point. So is the swivel. These small pieces of hardware carry the full load, and they are inspected as carefully as the anchor itself.
Choosing the Right Type
No single anchor is best for every situation, because the holding power depends on what the bottom is made of. In soft mud, a broad-fluked design that can bury deep works well. On rock or coral, a heavy hook-style anchor that snags a crevice may hold better than one designed to dig. Sand suits most modern plow and fluke anchors, which set quickly and hold firmly.
Size and weight still matter, but mainly for getting the anchor to the bottom and helping it set. Beyond that, the shape of the flukes and the length of chain a vessel can deploy decide how much holding power is available. A small boat in a sheltered harbor and a large ship in an exposed anchorage face very different demands, and their ground tackle reflects that.
If you are outfitting or checking a vessel, start with the seabed where you actually anchor most often, then match the anchor type and chain length to it before worrying about anything else.