When it comes to dive fins, few names are as respected among technical divers as Apeks. Durability, power, and precision control, Apeks fins have become a benchmark in both recreational and professional diving. Two models currently making waves are the Apeks RK3 and the Apeks RK4. Both deliver incredible performance — but they’re designed with slightly different divers and environments in mind. When diving with and chatting to many technical (and recreational) divers across the world, a lot of people kept refering back to these two fins in particular, and so I decided to give them both a test for myself.

Let’s dive into the details to help you choose the fin that fits your diving style best. First, I will start with comparing benifits divers may look for:

Both fins share Apeks’ signature vented blade design, which helps reduce drag on the upstroke and increase thrust on the downstroke. However, the RK3 and RK4 differ slightly in build and feel.

• RK3: Constructed from a durable thermoplastic rubber, the RK3 is built to withstand rough conditions. It has a short, wide blade that delivers excellent manoeuvrability and stability — especially in currents or when diving with heavy gear. The foot pocket is oversized, making it ideal for drysuit boots or thick neoprene.


• RK4: The RK4 builds on the RK3’s legacy but in a more compact, technically refined form. It features a one-piece rubber construction and a slightly shorter, stiffer blade, offering better control in tight spaces such as wrecks, caves, or when performing precision fin kicks.

Both fins excel in delivering balanced propulsion and control, but they have slightly different personalities underwater:

• RK3: Known for its powerful thrust and predictable handling, it’s a reliable all-rounder. It performs best in open-water and mixed-condition dives where a strong kick is needed, and is ideal for both recreational and technical divers. When testing them for myself, I found that they were a great option for shore entries and relaxed reef dives, and they did perform well in current, leaving my legs still feeling strong after the dives. They were less precise when I did a wreck dive, as they did not feel as snug on my feet as the RK4s.


• RK4: This fin takes finesse to another level. The shorter blade gives it superb control in confined environments, making it perfect for cave, wreck, and technical divers who need precise buoyancy and positioning. Despite being compact, it still packs plenty of thrust thanks to its efficient vented blade system and its design also allows for easy back-kicks and frog-kicks. Shore entries were clumsier with these fins as they are heavier, and my legs got slightly tired if I kicked a lot, but they allowed me to have strong short bursts of power when I needed it in the current. Also, when diving into wrecks, swimthroughs and caverns, I had incredible control and barely kicked up any silt!

In terms of buoyancy, the RK3 comes in both standard and HD versions, with the HD model offering extra stiffness and slightly negative buoyancy — perfect for drysuit divers. The RK4 sits closer to neutral, offering balanced handling whether you’re in a wetsuit or drysuit.

• Choose the RK3 if: You’re after a rugged, dependable fin for a variety of diving conditions for any level of diving. In my opinion, it's ideal for divers who prioritize thrust, durability, and a fit that accommodates heavy boots or drysuit gear, but is light enough to travel with.


• Choose the RK4 if:  You’re a technical diver or wreck enthusiast who values precise movement and control. I'd say that they are tighter, and offer exceptional handling in confined environments or when you need to minimize silt disturbance.

Both fins live up to the Apeks reputation for quality. The RK3 is the tried-and-true powerhouse that’s proven itself in military, rescue, and technical settings. The RK4 refines that legacy — compact, agile, and built for precision.

Whether you’re exploring open reefs or navigating the narrow corridors of a wreck, both fins deliver performance you can rely on. The real question is: Are you a power diver or a precision diver?

Still unsure and want to see more options? See our Best Scuba Fins of 2025 guide here.