When it comes to floating docks, most people just think “those black plastic boxes that make docks float.” But there’s a lot more to them than meets the eye. Here are five facts about dock floats that might surprise you—and give you a new appreciation for the technology that keeps your dock high and dry:
1) Dock floats are a relatively new invention!
Not too long ago, people literally tossed chunks of styrofoam under their docks and hoped for the best. It worked… sort of. The problem? Waves, wildlife, and weather quickly broke the foam apart, releasing tiny bits of pollution into the water. It looked bad, hurt the environment, and didn’t last long. Modern dock floats solved this problem by sealing the foam inside a tough, protective shell—clean, durable, and built to last.
2) The plastic shell doesn’t actually float.
That heavy-duty outer shell isn’t what gives your dock buoyancy—it’s the foam inside that does all the work! The shell’s job is simply to protect the foam from UV rays, impacts, and the elements. Without that shell, the foam would break down fast. So while the shell doesn’t keep your dock up, it makes sure the float can do its job year after year.
3) Dock float shells are made using the same process as playground slides and kayaks.
Most high-quality dock floats are created using a technique called rotational molding. It’s the same process used to make playground slides, plastic kayaks, and other big, seamless plastic objects. The result is a one-piece shell with no seams or weak points—super strong, uniform, and watertight.
4) The foam inside starts as tiny beads.
Inside every float, you’ll find expanded polystyrene (EPS) foam that started as small beads. During manufacturing, these beads are steamed inside the mold, expanding until they fill the entire cavity. That process creates a perfectly fitted, dense core that maximizes flotation and even keeps most water from seeping in.
5) Dock floats need to breathe!
This one surprises almost everyone—dock floats can actually crack or swell if they’re left sealed and sitting out of the water too long. Inside the shell, temperature and air pressure can build up as the float heats and cools in the sun. That’s why we leave one cap off and include vent plugs (you’ll find them taped to the side of your float’s rivet). Once the float is in the water (which regulates the float's temperature), you can seal it up with the vent plug so it stays stable and performs perfectly.
Modern dock floats are a small engineering miracle—strong, reliable, and much more eco-friendly than the old foam blocks of decades past. Whether you’re replacing old floats or starting your first DIY dock project, understanding how these work will help you build smarter and make your dock last longer.
Need help picking the right floats or hardware for your project? Contact us and we’ll be happy to help you find exactly what you need.