Table of Contents

Physics of Surfing

Most people never really stop to ask: what lets us surf a wave in the first place? From paddling in to carving turns, there’s a lot of physics working behind the scenes. Here’s a breakdown of what’s happening:

When you paddle for a wave, the water begins to slope upward, creating an incline. This incline allows you to tap into gravity. Without gravity pulling you down the slope, you wouldn’t even catch a small two-foot wave.

As the wave steepens, the gravitational pull increases, accelerating your speed. Eventually, your velocity matches that of the wave. Once you’re on your feet, you drop down the face of the breaking wave (gravity again!). At the bottom, you perform a bottom turn to redirect yourself. This maneuver sheds some of your speed.

Meanwhile, the wave continues to move toward shore (and you). It begins lifting you back up the face. Now you’re gaining potential energy (thanks to elevation) and still holding onto some velocity. As you angle your board back down the wave, gravity converts that potential energy into kinetic energy.

At this point, you’ve built up enough momentum to start performing maneuvers without the wave outrunning you. In a way, gravity gives you free energy to ride, sort of like skiing, except your “ski lift” happens as you’re riding down the mountain, not after.

And if you’re pumping a shortboard, you’re generating speed by shifting from low-energy zones to high-energy ones using your own movement rather than relying on the wave itself. (This also conserves energy compared to turning up the wave against gravity.)

Surfboard Terminology Defined

  • Lift and Buoyancy
    Once your surfboard gains enough speed, it starts generating dynamic lift. This type of lift is different from buoyant lift, which depends on the board’s volume (size and density) and acts as a static upward force. Both forms of lift point in the same direction (upward), perpendicular to the surface of the water. To get a feel for dynamic lift, think about airplane wings. While stationary, wings don’t produce lift because no air flows around them. But as the plane accelerates down the runway, airflow increases. Thanks to their angle of attack (or design asymmetry), the wings redirect air downward, creating lift in the opposite direction. The amount of lift depends on three things: the wing’s angle of attack, its velocity (which drives airflow), and pressure differences above and below the wing (less relevant for surfboards). A larger wing pushes more air down and generates greater lift at a given speed. Now let’s bring that idea back to surfboards. For boards, angle of attack comes from the rocker, while surface area comes from the combination of length and width. Velocity is largely dictated by the wave being surfed. So when do you want more or less dynamic lift? It depends on the wave. Surfboards are always a compromise between speed, control, and responsiveness. In powerful waves, a flatter, wider board can make things harder. You may find yourself drifting too far out on the shoulder right after dropping in. A board with less surface area helps you grip the wave’s face and stay closer to the pocket. On the flip side, weaker waves require more surface area to help you plane across the water and avoid bogging during maneuvers.

  • Drive
    Drive is one of the most talked-about features in surfboard design—and easily one of the most misunderstood. For some people, drive just means speed: if a board feels fast, it must have drive. For others (myself included), drive refers to how well a board responds when you ask it to accelerate, such as pushing on the tail during a turn and getting that extra burst of speed. Here’s why that second definition makes more sense to me. Speed usually comes from a lack of drag. The wave and gravity set the upper limit for how fast you can go, and the board’s design, especially how well it releases water, determines how close you can get to that limit. That kind of speed is great, but modern performance surfing demands more than just passive velocity. You also need to actively accelerate at key moments, like driving out of a bottom turn or powering through a cutback. So, for this website, let’s define drive as: a surfboard’s ability to accelerate in response to rider input. And speed as: how fast the board moves when riding in trim.

  • Pivot
    Pivot is one of those terms that gets tossed around a lot, but not always consistently. You’ll hear it used to describe how well a surfboard maneuvers in tight spaces, like turning quickly in the pocket. That definition isn’t wrong, but I lean toward a more specific interpretation. For me, pivot refers to how easily a board transitions from one rail to the other. Twin fins are a great example, as they tend to offer the most pivot of any fin setup. That’s because their design allows the board to roll and redirect with minimal resistance, making quick rail-to-rail changes feel fluid and intuitive. Understanding pivot in this way helps when evaluating a board’s responsiveness. One of the issues people have when surfing a thruster is pushing the center fin through turns. That takes strength and technique that lots of beginner surfer don’t have. Twins and quads lack a center fin and therefore power through turns easier. They also go rail to rail easier without the center line bias of a center fin.

  • Volume
    Volume is the outcome of multiple design decisions the shaper makes around plan shape and foil. These all come together to determine the overall 3D space the board occupies. This measurement directly influences the buoyancy of the board, or what’s known as static lift. Because most surfboard blanks use similar density foam, volume ends up being the key factor in determining how well a board floats. When choosing a shortboard, especially, it’s important to match the board’s volume to your body weight. That balance ensures the board floats you adequately and responds as intended. Years ago, Whitney Guild explored this relationship by surveying surfers across different skill levels. His research revealed that people in similar cohorts tended to favor boards with similar volumes. That work laid the foundation for many of the volume calculators you now see on surfboard brand websites (eg. Lost).

Board Characteristics

  • Rocker

Rocker refers to the curve of a surfboard when viewed from the side. You’ll often see it measured at the nose and tail. These numbers show how far each end of the board rises vertically from the midpoint. It might sound technical, but it’s one of the most intuitive design features once you connect it to how waves behave. Every wave has some degree of curvature, though that curve can vary wildly depending on the break. Take Virginia Beach, for instance: waves there tend to be more sloping and drawn out. Contrast that with spots like Hatteras or New Jersey on a solid swell, were they often produce steep, square barrels. It makes sense, then, that the rounder the wave, the more rocker you’ll need. A board with greater rocker fits better into the curve of the wave face, helping you maintain control and avoid burying the nose. On the flip side, flatter waves generally call for less rocker to keep speed and glide up. That balance plays a big role when you’re choosing a board or building a quiver tailored to your local surf conditions. Usually, small and mushy waves work best with boards that have less rocker. Bigger, more powerful surf demands more rocker to manage speed and maintain maneuverability. But there are days, especially in the colder months, when small waves still offer steep sections or small barrels. In those cases, choosing a groveler with more rocker can be helpful.

  • Plan Shape

Plan shape is the board’s outline, its length, width, and how that surface area is distributed. While shape impacts drag (elliptical outlines reduce it best), the real importance lies in how the board handles based on where that width shows up.

If the board’s widest point is pushed forward (a popular modern feature), you get more nose area and a narrower tail. This adds paddling ease and stability, especially when paired with flatter rocker. It suits longer-period, mushier waves but sacrifices some maneuverability. Boards with the wide point shifted back increase tail area and reduce nose volume. These are more agile, especially for tighter turns, but can feel twitchy in short lengths. Centered wide points balance the trade-offs.

Parallel outlines (straighter rails) tend to be faster and more stable, helping with paddling and drive. Curvier outlines—common on shorter, wider boards—plan earlier and lift more easily at low speeds. Boards with higher width-to-length ratios generate dynamic lift more efficiently, but they’re often slower in trim.

  • Rails

Surfboard rails play a significant role in how user friendly your board will be to surf. Rail design for small wave boards will tend to be more full or “boxy” and will have an apex more centered (eg. 50/50 or 60/40) relative to a performance oriented rail. This design wants to stay out of the wave face and is less likely to stick or bog when you are at a lower speed. Most daily driver and performance boards tend to feature medium rails with or without a tucked edge. The apex will generally be described as 60/40 or 70/30 througth the mid-section of the board which will then transition to 80/20 w/ a tucked edge to a true hard rail in the tail section. Virtually every shortboard will have hard rails in the tail section of the board starting a little in front of the side fins. This facilitates release and decreases drag.

  • Foil

Foil refers to how thickness is distributed along a surfboard, from nose to tail, and from the center stringer out toward the rails. Most boards gradually taper at both ends, becoming thinner toward the nose and tail. They also slim down toward the rails, which helps the board engage the wave face for better grip and control. This thickness profile plays a key role in performance and contributes to the board’s overall volume when combined with the plan shape. Some designs feature dramatic foiling, like retro fish-style boards, which are thickest under the chest and then quickly narrow toward the nose and tail. These boards can feel lively and sensitive but may be tricky for less experienced surfers. More user friendly boards tend to have even foiling, where thickness transitions more gradually across the length and width. That consistency makes the board more predictable, balanced, and easier to handle.

  • Bottom Contours

I don’t want to get into the different variations of bottom contours as that information exists in plenty of places. Rather than discussing bottom contours, specifically concave, in terms of lift and drive, I prefer to discuss them in terms of directionality. To me, the main effect of concave is the directionality that it creates relative to a flat or convex bottom.

To understand this, we need to think in terms of how water releases from the bottom of the board. The relative water flow over the bottom of a surfboard is always closer to parallel to the stringer than perpendicular to it (unless you’re sliding out). With the influence of rocker, there is always some rearward release from any point on a flat bottom surfboard. This is also true of convex shapes. However, with concave, this isn’t the case. Concave holds onto the waterflow longer than a flat board, which creates a degree of grip on the wave face as well as some drag. The grip created from concave (eg. “catching” more water flow from the wave) is what gives the feeling of lift when we unweight while pumping or coming out of turns. Concave also creates some grip during turns and is often featured on finless boards.

Depending on the type of surfing you do and the waves your region gets, concave can be a better or worse design choice. Without getting too into the weeds, think of concave as being fed from the power of the wave. The more steep and hollow the wave, the more concave can benefit you. Concave also tends to work better in shorter waves, where you have to create speed quickly. On longer waves, like Uluwatu, where you have plenty of time to get to speed and hold onto it, flatter designs can actually work really well. That isn’t to say a flat board can’t work in weaker beach break. In waves where it’s hard to generate speed (small and slopy), a flat board can reach a higher top speed, which may benefit you more, depending on what you’re looking for.

Wave Characteristics

Board design plays a huge role in how a surfboard performs, but understanding the waves you’re riding is just as critical. Even small waves can vary dramatically in shape and power. On the East Coast, winter swells around stomach to chest high can still pack plenty of punch, often appearing steep and hollow. At other times, even large, powerful swells may break soft and slopey. That’s why it’s essential to choose a board that matches the wave conditions and not just the wave size.

Working with a local shaper has distinct advantages as they understand your regional surf and can design boards that perform well in those conditions. While shapes from places like California or Hawaii can definitely work, East Coast surfers benefit from tailoring their quiver to seasonal patterns.

Here’s a general breakdown:

  • Summer: Mostly short-period windswell, usually under chest high. Waves are softer, favoring longboards or grovelers for better glide and planing.
  • Fall: Tropical systems begin forming and bring longer-period swell. September through November tends to deliver faster, more powerful waves with improved shape. This period is ideal for transitioning to higher-performance boards.
  • Winter: Nor’easters generate stronger storms and heavier surf. Swell periods typically range from 8 to 12 seconds, with stomach-to-overhead waves being more frequent. Hollow conditions call for performance boards that offer control, speed, and responsiveness.
  • Spring: Shoulder season between winter and summer. Gets swells that vary between the two.

Choosing a Board

Surfboard design is all about compromise. The best board for you depends on both the waves you surf and your personal style. On the East Coast, wave conditions vary widely, from soft summer mush to heavy winter barrels, so having a small quiver of boards makes a big difference.

For weak, mushy waves (summer and soft winter days), go with boards that have more surface area, flatter rocker (especially in the nose), and softer rails. The Lost Hydra is a great example: 5’5” x 20½”, wide tail block, flat rocker—plenty of lift for small surf and still duck-diveable thanks to lower volume.

For in-between waves (steep but not barreling), look for moderate rockers and slightly narrower outlines. My go-to is the New Toy by Surf Prescription Surfboards (5’10” x 19¾”). It planes well through flat spots and stays manageable in punchier sections, which is ideal for typical East Coast setups with variable wave shape.

For hollow, powerful surf, performance shortboards with higher rocker and narrower tails shine. Boards like the Rozbern Hound or Xanadu Nitz handle strong currents and steep takeoffs better. I prefer lower volume to keep duck diving easy and find they respond better in tight sections where timing and technique matter more than paddle power.

Fin Selection

Choosing the right fins is an essential part of surfboard setup, yet it’s often overlooked. Fin performance depends largely on size, flexibility, and how they interact with the tail shape and rocker of your board. The right set of fins will allow your board to work best while a bad set of fins can turn any board into a dog.

Flexibility and Materials: Fins range from soft plastic to high-performance materials like G10. More flexible fins tend to feel “smaller” in the water and have built-in washout due to flex, allowing for longer hold during turns. However, they don’t respond as quickly. Flex preference is personal, with some surfers finding softer fins easier to pump in small waves, while faster boards often benefit from stiffer fins that react quickly in maneuvers.

Tail Shape and Fin Size: Tail surface area dictates how much control fins need to provide. Wider tail blocks (like square or rounded squash tails) usually require larger fins. Narrower or pulled-in tails may work with slightly smaller fins, but larger fins are still often preferred for added control.

Rocker, Fin Shape and Tail rocker influences:

  • Boards with more tail rocker tend to pair well with raked fins (swept-back designs) for added hold and drive.
  • Flatter rockers—like on grovelers—respond better with upright fins, which improve pivot and tight turning.

Quad Setups and Keels: Flat grovelers with quad setups often benefit from split keel-style fins—larger, raked front fins combined with smaller, upright rear fins. This enhances lift and control without overpowering the board’s compact shape.

Recommendations and Starting Points:

  • It’s smart to own multiple fin sets, especially those that have worked well with past boards. If you’re just starting out:
  • Try a set of large, neutral-template honeycomb fins (like the Futures F8) if you’re over 170 pounds or riding boards with wider tails. These have three equal-sized fins and offer reliable baseline performance.
  • For boards surfed in small waves or with wider tails, consider sets like the AM series, which feature large side fins and a smaller center fin to reduce drag and improve release.
  • On the East Coast, particularly at beach breaks in New Jersey or the Outer Banks, upright fins tend to work well. They’re great for pockety waves and offer maximum sensitivity.