<aside> 🌊 These are the more nuanced tweaks to a skimboard that impact a boards performance. While shape is the most significant factor in influencing skimboard behavior, these features are important in complementing a shape to optimize effectiveness.
</aside>
Rocker is the curvature on a board which ultimately effects speed and maneuverability of a board. Generally a flatter beach will call for less rocker while a steep beach will call for more rocker. It is important to note that boards are not in the shapes of bananas and require a flat spot in the middle to adequately maintain speed while sliding.
Graphic from Victoria Skimboards
Graphic from Skatepro
Nose Rocker Rocker on the nose controls how the nose enters the incline of face and also how a board can transition smoothly over bumps or rushing water. Nose rocker generally sits around 2". In large conditions it's worth considering more rocker to navigate steep faces. A larger nose rocker lets the rider sit lower on the board and have more dynamic control when navigating waves.
For reference, Victoria standard rocker is 2", and Exile standard rocker is 2.25". These are just standards, they offer different selections.
Tail Rocker To turn your skimboard you will transition your weight to the back to engage your boards tail and guide your nose. Tail rocker is mostly responsible for your maneuverability, allowing to better control your turns and speed in fast sections. Some brands offer 0" rocker in the tail which emphasizes speed, but it is advisable to have at least a bit of rocker to facilitate turning. That being said, no tail rocker will provide additional speed when planing.
For reference, Victoria standard rocker is 1/16", and Exile standard rocker is 1/8". These are just standards, they offer different selections.
Thickness mostly comes down to preference, but is worth talking about in weaker conditions where you want a thicker board. A thicker board will offer more buoyancy, but much less so than shape would. If you want a board that floats, you should be getting that float from shape and not thickness alone.
5/8" thickness is the thinnest standard core offered and is noted as the most responsive.
3/4" thickness is the thickest standard core offered. It is stronger and offers slightly more float in exchange for response.
3/4" tapered to 5/8" is offered by brands as a middle ground where the middle section is 3/4" for float and the thickness tapers to 5/8" at the boards ends to try to achieve the maneuverability of a 5/8". Board tapering is great for maintaining mid section thickness while allowing you to rock onto the thinner tail and nose for maneuvers, allowing for a surf line experience. Best of both worlds, most say.
In the end, 3/4" doesn't imply you're getting a log, and 5/8" doesn't imply you're skimming on paper. They're relatively similar measurements, but they do feel different in hand and perform different in the water. Complement this feature to your shape and conditions. If you're in large California waves you probably want to aim for a thinner board. If you're dealing with below-average conditions you may want to considering adding thickness to your shape to really push off the mush. Often a preference, this will not make or break your board.
Rails affect how you turn, float and hold speed on a face. Generally speaking, the more the rail tapers the more speed and response the board will have. A boxy rail might be slower and less sensitive, but more stable and consistent.
Boxy rails: forgiving turns by being more slow and controlled.
Tapered rails: Grip wave faces better, giving more response and speed due to their sharpness.
Images from Victoria Skimboards