What is an Anchor?

Ian Fortey by Ian Fortey Updated on January 19, 2023. In Boats

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An anchor is a tool used to secure a vessel in the water. Depending on the type of anchor it can achieve this goal in a variety of ways but, in general, the anchor will grab onto the seafloor or embed itself by the use of flukes, grapples or other protrusions. Since the anchor will be attached via a line of some kind to the boat itself, the boat will be moored in place with a limited range of movement for as long as the anchor remains secure.

What are the Different Anchors?

Anchor is a remarkably general term for what any given boat may have on board in the present and certainly through history. So while “something that holds a boat in place” is a very general answer to the question of “what is an anchor?” there are still a number of more specific ways that question can be addressed based on the type of anchor we’re talking about. 

There are literally dozens of not hundreds of anchor designs but the basic types are a little simpler to understand. How they work helps define what they are and what makes them different from one another, so let’s check out some of the basic anchor types. 

What is a Fluke Anchor

SeaSense Slip Ring Fluke Anchor

This common anchor type uses flukes, which are pointed projections like teeth, to dig into the sea floor. Designs may vary but in general there are at least two flukes that will scrape along the seafloor as the anchor rode applies tension until they embed themselves and are able to hold the boat. These anchors work best in muddy and sandy conditions but will not perform as well if the seabed is rocky or littered with things like debris or weeds since the flukes will not be able to get a firm purchase. You might hear these called Danforth anchors.

Simple Definition: A fluke anchor is an anchor with flukes or teeth that digs into the ocean floor to hold a boat in place. 

What is a Plow Anchor

A plow anchor is similar to a fluke anchor but it has a single, center fluke which resembles an old time farming plow, hence the name. The point of the fluke has some good weight behind it to allow it to dig in deeper than a lighter anchor might. This means they can set fairly quickly and offer a good hold in most seabeds, though they probably will struggle if the ocean floor is some kind of hard clay. Another potential issue with this kind of anchor is that they tend to be somewhat bulky and hard to store. These are also sometimes known as CQR anchors.

Simple Definition: A plow anchor is an anchor with a single fluke, shaped like a plow, that can embed itself in the seafloor to hold a vessel in place.

What is a Claw Anchor

Claw anchors are similar to plow anchors but with a broader scoop portion like a shovel and three claws. They can also set quickly and are good for most soft bottoms as well as things like coral and rocks. Hard clay will still be difficult and they have trouble setting into weeds as well. These are, if not as popular as fluke anchors, certainly very close thanks to their versatility. 

Simple Definition:A claw anchor is an anchor with three claws that allows it to dig into the ocean floor and provide holding power for a boat.

What is a Mushroom Anchor

Mushroom anchors have no flukes at all and these tend to work best as long term mooring rather than short term stay. Once the anchor hits bottom the current will, over time, deposit silt and mud inside the mushroom cup, slowly burying it and giving it more strength and holding power. They use these for buoys and while they can work for small boats, they’re not ideal. 

Simple Definition: Mushroom anchors are shaped like upside down mushrooms and provide a cup that can fill with debris and mud from the seafloor, slowly burying itself to provide long term mooring for something like a buoy or small boat. 

What is a Box Anchor

Box anchors are much newer in the anchor world and are not all that common. They get the name from the  fact they do resemble metal box frames with flukes on the top and bottom of two sides.

Box anchors are touted for the ability to set pretty much instantly once they reach the bottom with very little effort involved. They hit the seabed, flip as the rode pulls and grows tense, and then set into place immediately.

What is a Grapnel/Grappler Anchor

Crown Sporting Goods Galvanized Grapnel Anchor

These anchors look like grappling hooks which makes them certainly interesting and  unique. They are ideal for rocky bottoms as the flukes can get wedged into the rocks to hold the boat in place. They tend to come free fairly easily if the current and winds change and they don’t do well for long term mooring.

Simple Definition: A grapnel anchor is a hooked shaped anchor that can wedge itself into rocks or other large debris on the ocean floor to moor a vessel in place.

What is a Sea Anchor

By Ed Dunens – Sea anchor, CC BY 2.0,

A sea anchor is unique insofar as this kind of anchor doesn’t actually grab hold of anything. It works a bit like a parachute and is most often used by boats during poor weather. The anchor streams behind the boat and works like a water brake. It provides drag to slow the progress of the boat without mooring it firmly in place like a traditional metal anchor would. The purpose of this kind of anchor in bad weather is to prevent the boat from being tossed by the waves and even overwhelmed by them. 

Simple Definition: A sea anchor is more of a water brake or parachute designed to slow a vessel and limit movement during poor weather and on rough seas.

What is a Shallow Water Anchor

Shallow water anchors are often just poles. There are mechanical rigs that can allow these to work by use of a mechanical arm that raises and lowers the pole, or some boaters choose to make their own as they are simple and easy to use rigs. Essentially all that is needed is a pole that is both sturdy enough and long enough to be planted into the seabed below the boat through some kind of ring or clamp that holds it to the hull of the vessel. Because they’re meant to be used in just a few feet of water, they pin the boat in place like setting a stake for a tent and can easily be dislodged by handle.

Simple Definition: A shallow water anchor is a pole that can be planted directly into the seabed when a boat is in just a few feet of water that holds the boat firmly in place and doesn’t allow for drifting at all.

A Note on Anchor Shapes: Admiralty Anchors

These are the most recognizable shaped anchors, that traditional anchor shape you’d see in drawings, cartoons and tattoos which features a center shaft with a pair of arched arms at the bottom in a vaguely crescent shape. You don’t actually see these kinds of anchors much in real life anymore because they’re not the best design anymore. The big problem with these anchors was the stock across the top.

When a ship dropped anchor using this type, it would fall to one side on the ocean floor. As the boat continued to drift the stock, that narrower crossbeam across the top where the chain is connected, dug into the seabed and caused the anchor to flip. Then one of the large flukes would be forced to dig into the seabed.

One of the flukes would always be up but the other could dig in deeply. This type of anchor held well but the anchor rode or chain would get caught up in the stock if the current or winds changed and could pull the anchor free so it needed to be reset. Also, it was much harder to stow this kind of large anchor. 

What is The Anchor Rode?

Your anchor needs to be attached to your vessel with a line, typically called a rode. The rode can be chain, rope or a combination of both. On very large vessels anchors are always held with chain because of the sizes and weights involved. However, with smaller fishing boats and similar vessels, the road is often best served by being a combination of the two. On exceptionally small boats, a simple rope will suffice for an anchor rode provided it’s still properly secured. 

When you drop anchor, the rode will run out with the anchor and leave a substantial amount of slack on the vessel. Once you have the ship anchored, the rode is what applies that tension that allows the ship’s anchor to embed itself.

The Bottom Line

An anchor is a device that enables you to secure your boat in place while at sea. Once dropped, it sinks to the bottom of the body of water and the movement of your boat will apply tension to the line, causing the anchor to dig into the bottom and grab hold with the use of things like flukes or claws, depending on your anchor type. Different anchors excel at holding a boat in different conditions and in different materials such as claw, sand, rocks or weeds. 

About Ian

My grandfather first took me fishing when I was too young to actually hold up a rod on my own. As an avid camper, hiker, and nature enthusiast I'm always looking for a new adventure.


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