Apeks Diving Fins

Apeks Diving Fins — Military-Tested, Diver-Proven

The Apeks RK3 fin has one of the clearest origin stories in diving equipment. Developed in collaboration with the US military and based on one of the first vented rubber fins sold in North America, the RK3 design has been standard-issue gear for military special operations units, coast guard divers, and public safety dive teams for decades. That heritage shows in the construction: these are uncompromisingly rugged thermoplastic rubber fins, built to hold up in the toughest underwater environments, temperatures, and conditions that recreational fins simply aren't designed for.

At DiveCatalog.com, we carry the full Apeks fin lineup in multiple sizes and colors: the standard RK3 and the stiffer, negatively buoyant RK3 HD, both open-heel designs with spring straps as standard.

RK3 vs. RK3 HD — Understanding the Difference

Apeks RK3

The standard RK3 uses a medium-density thermoplastic rubber that is neutrally to slightly positively buoyant. This makes it well-suited to warm-water recreational diving where you're wearing a wetsuit with minimal buoyancy, and to divers who want a lighter fin that travels well. The RK3 comes in Black and Pink colorways and four sizes (Small through Super/XL). The foot pocket is generously sized to accommodate wetsuit boots, and the spring strap system allows easy donning and doffing with thick gloves.

Apeks RK3 HD

The HD (High Density) version uses a denser thermoplastic rubber that is stiffer and negatively buoyant. This makes it the preferred choice for drysuit divers — the negative buoyancy helps offset the positive buoyancy of a drysuit and thick dry boots, and the stiffer blade provides more propulsive force per kick. The extra density also means the RK3 HD performs particularly well in current and when wearing heavy exposure suits. Available in Black and Orange.

What Makes the RK3 Different

The short, wide blade geometry is intentional and well-thought-out. Short blades provide maximum forward thrust with great maneuverability — useful in confined spaces, current, and for divers who need precise control rather than raw speed. The vented blade design reduces resistance on the upstroke and enhances thrust on the downstroke, and the vents eliminate the vortexes that occur along the back of a solid blade — similar in principle to how split fins work, but in a traditional rubber construction that is far more durable.

The oversized foot pocket is one of the RK3's most practical features. Because the fins are regularly used with both neoprene wetsuit boots and drysuit rock boots — which take up very different amounts of space — Apeks deliberately made the pocket accommodate the widest range of footwear. Two large grommet holes on the blade allow the fins to be clipped to a carabiner for easy storage when entering the water from rocks or boat ladders.

Spring straps are standard on both models. The custom-designed buckle holds the spring strap in the optimum position, and the simple push-pin design allows strap replacement without tools — useful for working divers and professionals who need field serviceability.

Who Are Apeks Fins For?

Diver Type	Recommended Model	Why
Warm-water recreational divers	RK3 (standard)	Neutral buoyancy, lighter weight, excellent propulsion in wetsuit boots
Cold-water & drysuit divers	RK3 HD	Negative buoyancy offsets drysuit; stiffer blade, large foot pocket fits rock boots
Technical divers	RK3 HD	Rugged, controlled blade; good for frog kick and modified flutter; carabiner holes for staging
Military & public safety divers	RK3 / RK3 HD	Standard-issue for military and coast guard; purpose-built for harsh environments
Instructors & divemasters	RK3 HD	Field-serviceable spring straps; durable enough for daily professional use

A Note on Sizing

Apeks doesn't publish shoe size charts for the RK3 fins, and for good reason: the right size depends on what footwear you'll be wearing inside the fin. A size 9 foot in a thin neoprene wetsuit boot needs a different fin size than the same foot in a heavy drysuit rock boot. Apeks recommends trying the fins on with your actual diving footwear where possible. If you're unsure, contact our team and we can help guide your sizing decision based on your boot type and normal shoe size.

Why Buy Apeks Fins from DiveCatalog.com?

Authorized Apeks dealer — full manufacturer warranty
RK3 and RK3 HD available — multiple sizes and colors, browse the collection above
Expert advice — we can help you size correctly for your boot type
Fast shipping — most in-stock sizes ship within one business day
Rewards program — earn points on every purchase

Frequently Asked Questions — Apeks Fins

What is the difference between the RK3 and RK3 HD?

The material density. The standard RK3 uses a medium-density rubber that is neutrally buoyant and slightly more flexible. The RK3 HD uses a denser rubber that is negatively buoyant and stiffer. For drysuit diving, the HD is almost always the better choice. For warm-water wetsuit diving, the standard RK3 is the more common pick.

Are the RK3 fins suitable for cave diving?

Yes. The RK3's short blade and solid rubber construction make it popular with cave and overhead environment divers. The compact blade is maneuverable in confined spaces, and the negative buoyancy of the HD version helps with trim in a drysuit. Many technical and cave divers prefer a shorter rubber fin over longer composite paddle fins specifically for control in tight environments.

Can I replace the spring straps myself?

Yes. The spring straps use a simple push-pin design that allows replacement without tools. Replacement straps are available separately if needed.

Do the RK3 fins work with a frog kick?

Yes. The short, wide blade geometry of the RK3 is well-suited to frog kicking — the technique preferred by many technical and cave divers for its low silt disturbance and efficiency in overhead environments. Both flutter kick and frog kick work effectively with the RK3 design.

What sizes are available?

The RK3 and RK3 HD are both available in Small, Medium, Large, and XL (Super). As noted above, sizing depends on the footwear you'll be using — contact us if you need help deciding.

Are Apeks RK3 fins good for travel?

The RK3 is more compact than most paddle-style dive fins, which helps with packing. The standard RK3 (neutral buoyancy, lighter) is the better travel choice. The HD adds weight due to the denser rubber, which may matter for airline baggage allowances.

If you want a fin that performs as well on a drift dive in the tropics as it does in a cold-water quarry with a drysuit and rock boots, the Apeks RK3 family is the benchmark. Browse the full collection above, and contact us if you need help with sizing or model selection.

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Extremely comfortable and ideal for FL

This one is super comfortable and is the perfect thickness for Florida weather

Great Knife that stays put

Absolutely love this knife. The holder is super tight and there is no chance that you accidentally loose it like with other knifes.

Well made, love that they don’t add buoyancy

Well made, love that they don’t add buoyancy.

Comfort From the Parking Lot to the Dive Site

The Scubapro Everflex 5mm Boot is one of the most comfortable dive boots I've worn. From rocky shore entries to long walks across the parking lot, the built-in arch support and sturdy sole make a noticeable difference.

The 5mm neoprene provides plenty of warmth without feeling bulky, and the side zipper makes getting the boots on and off quick and easy. Once paired with open-heel fins, they offer a secure, comfortable fit that stays put throughout the dive.

The rugged sole provides excellent traction on slippery boat decks and uneven shorelines, giving you extra confidence before you even hit the water.

They're not the cheapest dive boots available, but after a full day of diving, your feet will appreciate the upgrade. Your dive buddies may still complain about the walk to the water—but you probably won't.

Warm Hands Make Better Dives

The Waterproof G2 5mm Semi-Dry Gloves are some of the warmest and most comfortable dive gloves I've ever used. They do an outstanding job of keeping your hands warm without sacrificing the dexterity you need to operate clips, cameras, or your dive computer.

The pre-curved design feels natural from the moment you put them on, reducing hand fatigue during long dives. The semi-dry seals do an excellent job of minimizing water exchange, helping your hands stay comfortable even in colder water.

They're built with the same attention to detail you'd expect from Waterproof, with durable materials and reinforced palms that are made to handle years of diving.

They're not the least expensive gloves out there, but cold hands can ruin an otherwise great dive. With the G2s, you'll spend more time enjoying the underwater world and less time wondering if your fingers are still attached.