Boat Anchor Types Compared: Which Fits Your Boat?

Updated 6 November 2026 · Standard formula, shown below

This guide compares the most common boat anchor types—fluke, plow, claw, and mushroom—and explains which one suits your boat size and the seabed you anchor on. You’ll learn how each anchor sets, where it works best, and how to match it to your boat’s length and weight for a secure hold.

Why Anchor Type Matters

An anchor’s only job is to hold your boat in place against wind, current, and waves. But no single anchor works everywhere. A design that digs into soft mud may slide across a rocky bottom, and one that grips grass might not penetrate hard sand. The seabed—mud, sand, rock, grass, or kelp—determines which anchor can set and stay set. Your boat’s size and weight also matter: a small anchor on a large boat will drag, while an oversized anchor is awkward to handle and store.

The Main Anchor Types

Fluke (Danforth) anchors: Two flat triangular flukes that pivot on a shank. They dig deep into sand and mud but have little holding power in rock or thick grass.
Plow anchors: A single curved point that rolls over to set, like a plow. They work in sand, mud, and grassy bottoms, and reset easily when the wind shifts.
Claw (Bruce) anchors: Three curved claws that set quickly in most bottoms, including rock and coral. They hold well in variable conditions but may not penetrate thick grass as deeply as a plow.
Mushroom anchors: A dome-shaped head that relies on weight and suction. They are common for permanent moorings and small boats on soft mud, not for temporary anchoring in strong currents.

How Each Anchor Works

An anchor holds by digging into the bottom and creating resistance. The fluke anchor’s sharp points penetrate sand and mud, then the shank pulls the flukes deeper as tension increases. The plow anchor’s single point digs in and the weight of the shank keeps it buried. The claw anchor’s three points grip in multiple directions, making it forgiving when the boat swings. The mushroom anchor simply sinks into soft mud and the suction of the mud over the dome adds holding power.

The angle of the shank and the length of the rope or chain (called scope) also matter. A scope of 7:1 (seven feet of line for every foot of water depth) is standard for all-day anchoring. Without enough scope, the anchor is pulled upward instead of horizontally, and it will trip out of the bottom.

Choosing by Bottom Type

Sand: Fluke and plow anchors work best. Flukes dig deep and hold well; plows are nearly as good and reset more reliably.
Mud: Fluke anchors with wide flukes and a sharp point are ideal. Plows also work, but a fluke’s broad surface gives more grip in soft mud.
Rock and coral: Claw anchors are the most reliable because their points catch in crevices. Plows can work if there are gaps, but flukes will slide.
Grass and kelp: Plow anchors cut through vegetation and set below it. Claw anchors may tangle, and flukes often ride on top of the grass.

Boat Size and Anchor Weight

Anchor manufacturers provide weight charts based on boat length. For a 20-foot boat, a fluke anchor of about 8 to 10 pounds is typical. A 30-foot boat needs roughly 15 to 20 pounds. Plow anchors are often heavier for the same boat because they rely on weight to set. Claw anchors are usually lighter than plows for the same holding power. The chart on the anchor’s packaging or the manufacturer’s website is the best guide, but a good rule is to choose the next size up if you anchor in strong currents or heavy weather.

Common Problems and Mistakes

Not enough scope: Too short a line pulls the anchor upward. Use at least 7:1 in calm conditions, more in wind or current.
Anchoring on the wrong bottom: A fluke anchor on a rocky bottom will not hold. Check the chart or ask local boaters before anchoring.
Using a mushroom anchor for temporary stops: Mushroom anchors are for permanent moorings. They take time to sink in and can drag in a breeze.
Overloading the anchor: A small anchor on a big boat drags. Always match the anchor to the boat’s length and weight, not to the size of the anchor locker.

Costs and Alternatives

Prices vary widely by size and material. A 10-pound fluke anchor is often the least expensive, while a plow or claw of the same size costs more due to heavier construction. Stainless steel anchors are pricier than galvanized steel but resist corrosion. Alternatives include a grapnel anchor (a multi-pronged hook) for small boats in rocky areas, and a sea anchor (a drogue) that is not for holding in one spot but for slowing drift in a storm. For most recreational boats, a fluke or plow anchor is the best all-around choice.

Safety and Best Practices

Always attach the anchor line to a cleat or bow eye, not to the rail or a stanchion.
Use a length of chain between the anchor and the rope to add weight and prevent chafing on the bottom.
Before anchoring, check the depth and bottom type. A depth sounder helps, but a chart or local knowledge is more reliable for bottom composition.
When anchoring overnight, set a second anchor or use a heavier anchor to be safe.
Always wear gloves when handling anchor line, and keep fingers clear of the chain when raising the anchor.

Frequently Asked Questions

What is the best anchor for a 20-foot boat?

For a 20-foot boat, a fluke anchor of 8 to 10 pounds is a good all-around choice for sand and mud. If you anchor in rocky areas, a 10- to 12-pound claw anchor is better.

Can I use one anchor for all bottoms?

No single anchor works perfectly on every bottom. A plow anchor is the closest to universal, as it sets in sand, mud, and grass, and can work on rock if there are gaps. But for a dedicated rocky bottom, a claw anchor is more reliable.

How much chain should I use?

A common rule is to use a chain length equal to the boat’s length. For a 25-foot boat, use about 25 feet of chain. The chain adds weight, which keeps the pull horizontal and helps the anchor set.

What does scope mean?

Scope is the ratio of anchor line length to water depth. A 7:1 scope means 70 feet of line for 10 feet of water. More scope gives a flatter pull, which holds better. In strong wind, use 10:1.

How do I know what bottom I’m anchoring on?

Look at a nautical chart, which shows bottom types like sand, mud, or rock. You can also lower a weight on a line and feel the bottom, or ask local boaters. Some depth sounders show bottom hardness, but charts are the most reliable.

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.