Diver Propulsion Vehicles (DPVs) offers unparalleled speed and efficiency in diving. This guide covers their benefits, drawbacks, types, how to choose yours, courses, expert tips, and more.
Want to Glide Underwater? With a Diver Propulsion Vehicle, You Can!
Imagine effortlessly gliding across the seafloor, covering more ground without getting tired. That’s exactly what an underwater motor thruster, or DPV, can do!
I know because I’ve used several. I had to upgrade as I improved as a diver.
When I bought my first underwater electric motor, I was thrilled.
The promise? Covering vast distances and exploring those previously unreachable spots.
With an underwater propulsion device, long dives become a breeze, and the air consumption? It’s practically infinite since you’re not kicking.
Of course, it’s not all perfect. Underwater motors have their quirks. They need maintenance, cost a pretty penny, and most importantly, you need to know how to use them.
So, if you want to hear everything I’ve learned about underwater thrusters and scooters, keep reading.
A DPV, or Diver Propulsion Vehicle, is an underwater propulsion motor that allows divers to move more efficiently and quickly underwater. This device, also known as an underwater thruster motor, helps divers cover more distance with less effort, enhancing the diving experience.
The history of underwater propulsion motors is fascinating. They were first used during World War II! Yes, you read that right—they were adapted from torpedoes for secret missions. Later, technical divers adopted them for exploring deeper and more complex places. Thanks to technological advancements, electric underwater thrusters are now more accessible, and any diver can enjoy them!
No wonder these underwater motors provide faster and more efficient movement, which is useful for long dives and helps conserve air, extending your time underwater. They also add excitement to the experience and make it easier to explore hard-to-reach areas.
Today, Diver Propulsion Vehicles (DPVs) are widely used in recreational diving. Primarily, they enhance immersion time by either extending the dive’s range or increasing descent speed.
For divers with disabilities, these underwater thruster motors provide propulsion that their legs cannot. Technical divers also find underwater electric motors indispensable for managing heavy gear or large equipment. The underwater thruster motor effortlessly drags all that weight, making it ideal for strong currents, extending distances in confined environments (no cave is off-limits), and reducing dive times and decompression.
In scientific diving, explorers leverage the towing capability of this technology to gather data, create maps, and produce educational materials.
Using a Diver Propulsion Vehicle can significantly enhance your diving experience. Here’s why:
No, we don’t sell Diver Propulsion Vehicles, so we might be the only ones talking about the downsides of these gadgets.
Battery Dependence and Mechanical Failures: These underwater motors run on batteries, so battery life is crucial. You could run out of power mid-dive, and considering they are mechanical devices, they can fail—especially problematic during deep dives or cave explorations.
Risk of Collisions and Entanglements: DPVs, or high-speed underwater scooters, are fantastic for moving quickly underwater. However, that extra speed can turn you into a human torpedo. It’s easy to collide with rocks, coral, or even get tangled in marine life or lines. Imagine having to disentangle yourself from seaweed or, worse, a jellyfish—definitely not fun!
Rapid Ascents and Descents: Another thing to watch with these underwater thrusters is their tendency to shoot you up or down at high speeds. Experienced divers know this can be dangerous.
Using One Hand Less: Using an underwater electric thruster means you’ll have at least one hand occupied. This can be a bit inconvenient if you need to do delicate tasks like taking macro photos or handling other diving equipment. Not a deal-breaker, but definitely a minor hassle.
Feeling Colder: Since you’re not kicking to move, your body generates less heat. So, be prepared to feel colder, especially in cooler waters. Make sure to wear your suit!
Distraction and Extra Workload: Operating an underwater motor thruster isn’t just about turning it on and forgetting it. It requires attention, which can distract you from important things like navigation or keeping an eye on your dive buddies. A silly distraction underwater can get you into trouble.
Cost and Maintenance: These gadgets aren’t cheap and require good maintenance. From charging batteries to checking components, you’ll need to invest time and money.
Limitations in Strong Currents: If you dive in strong currents, the DPV can complicate things. Maneuvering an underwater motor thruster in these conditions requires skill to avoid being swept away (literally).
Thinking about getting one of these underwater propulsion devices? From basic handheld scooters to advanced personal underwater thrusters for serious divers, there’s a Diver Propulsion Vehicle (DPV) for every level of diving and budget. Here’s a rundown:
Mini or Recreational DPVs: Perfect for confined, shallow waters or exploring calm reefs. These come in two main types:
Advanced and Technical DPVs: Larger and more powerful. These require both hands to operate and can reach incredible depths with impressive speed.
Tow-Behind Scooters: These are like small torpedoes with protected propellers. Divers hold on and are zoomed through the water like superheroes. These electric underwater thrusters are extremely popular in both recreational and technical diving. Why? Because they are easy to use and incredibly efficient—think of it as having your own car to explore the ocean!
Commercial or Military DPVs: These are the heavyweights used for underwater tourism, boat inspections, scientific exploration, or military operations.
Swimmer Delivery Vehicles (SDVs): The top-of-the-line in underwater propulsion, SDVs are large, robust, and designed to carry multiple divers with all their gear. They’re the go-to for military, technical diving, and commercial operations. With one of these, you can cover vast distances underwater and carry everything you need without breaking a sweat.
Wet Subs: For those who need comfort and control underwater, wet subs let you sit or lie down, breathe from your tank, and cruise along!
Semi-Wet Subs: Explore the ocean without getting fully wet. They feature an air bubble that allows you to breathe and chat with other occupants. These are perfect for tourists who don’t have diving certifications but still want a taste of aquatic adventure!
Manned Torpedoes: Just like in James Bond movies, manned torpedoes are advanced underwater propulsion devices used mainly by the military for infiltration and reconnaissance missions. First used during World War II, these gadgets are the ultimate in underwater motor thruster technology.
If you are looking for more details, kindly visit Haoye.
Do you think you can just dive in with an underwater scooter and hope everything goes smoothly, or are you the type who prefers to know what they’re doing? Getting certified means you not only learn to use an underwater thruster motor but also ensure you’re up to date with all safety standards. Without proper training, you could find yourself in a bigger mess than expected, especially if something goes wrong underwater.
Top Agencies for Your Diver Propulsion Vehicle Certification
What Will You Learn in the Course?
Get Trained: Learn how to operate your Diver Propulsion Vehicle (DPV) like a pro and what to do if things get tricky. It’s crucial to manage your buoyancy while using an underwater thruster motor. Are you on top of it?
Practice on Land: Don’t dive straight in. Get comfortable with the controls and handling of your underwater motor thruster on the surface before you hit the water.
Plan Your Dive: Before you dive, plan your immersion carefully. Outline a clear route, set the maximum depth, and make sure everyone in your group is aware of the plan. Consider the battery life of your electric underwater thruster and ensure it’s enough for your planned time underwater.
Pre-Dive Checklist: Check the battery, test the gear, and have an emergency plan in place. Don’t leave anything to chance!
Follow Manufacturer’s Safety Instructions: Always adhere to the safety guidelines provided by the DPV manufacturer. This includes not exceeding the recommended depth and avoiding use in adverse weather conditions or strong currents.
Watch Your Depth: Don’t change depths too quickly. Underwater scooters can rapidly shift you up or down, so be cautious.
Be Aware of Your Surroundings: Keep an eye on everything around you—seaweed, fishing lines, and marine life. You don’t want to get snagged or hit.
Monitor Your Air Supply: Underwater thrusters can extend your distance, so keep a close watch on your gas supply to avoid running low unexpectedly.
Keep an Eye on Your Buddy: Maintain visual contact and stay close if possible. Communicate and ensure your buddy is comfortable using the underwater electric motor. Be ready to assist if needed.
Be Ready to Detach Quickly: Make sure you can release the scooter underwater fast if something goes wrong.
Prepare for Emergencies: Know how to stop the underwater propulsion motor quickly and have a plan for any equipment failures.
Maintain Your Equipment: After each use, rinse the DPV with fresh water to remove salt and other residues. Check the battery condition and ensure it’s fully charged before your next dive. Follow the manufacturer’s regular maintenance recommendations.
Do you have a Diver Propulsion Vehicle? Share your experience in the comments on Facebook!
Waterjets made a big splash, and now we see them on many high-performance craft. This prevalence of active installations prompts us to search for other applications. Can we put jets on a slow river boat? Or a fishing vessel at 20 knots? This article focuses on the merits of waterjets, with focus on the most important factor: efficiency.
Waterjets work by pumping a LOT of water through a closed duct. The acceleration of this water creates a forward thrust for propulsion. Figure 2‑1 shows a typical arrangement for a waterjet. Suck the water in at the bottom, the impeller adds power, and the nozzle accelerates the water out the back.
Waterjets operate completely different from propellers. A propeller tries to minimize the velocity change and focus on pure pressure differences. But a waterjet intentionally increases the velocity change between inlet and outlet. That change in momentum creates thrust. Multiply the thrust with a huge flow rate, and you get propulsion. This different paradigm leads to several differentiating features:
A waterjet is essentially a pump inside a very short pipe. Pumps work differently than propellers; they don’t show the same limits. Pump efficiencies around 90% or more are regularly attainable. In contrast, conventional propellers stop at 60%-72% efficiency. But waterjet efficiency involves more than just the pump. A host of factors reduce the efficiency:
The largest factor in waterjet efficiency is the ratio of velocity at the jet outlet to the inlet. This velocity ratio strongly influences the total efficiency because waterjets depend on high flowrates for efficient operation. Without any water acceleration, the jet fails to produce thrust. But if we force too much acceleration, the efficiency drops off fast. DMS contacted a waterjet manufacturer to obtain typical values for the velocity ratio. They rightly refused to disclose any information about this critical trade secret. Instead, DMS tested several velocity ratios to see how they impacted theoretical waterjet efficiency. (Figure 3‑1) These ratios were not based on any waterjet manufacturer.
A higher velocity ratio meant more acceleration and more thrust from a single jet, but at the cost of lower efficiency. The figure showed that changing the velocity ratio also impacted the range of efficient operation. A higher velocity ratio allowed the jet to maintain its efficiency across a wider range of ship speeds, but at the cost of lower peak efficiency. This variation in capabilities drove waterjet manufacturers to supply different models, targeted towards different speed ranges and power requirements.
In fairness to waterjets, we also need to remember the other drag elements required for propeller propulsion:
The waterjet sits flush inside the hull, with just one outlet. At speed, the exit nozzles completely clear the water. This reduces the total resistance on the vessel. We have no propeller shaft or shaft brackets to drag through the water. Another element removed: the rudder. Waterjets don’t need a rudder, because they direct the thrust through changing the direction of the outlet stream. Removing these elements already gives the waterjet an edge over propellers. But velocity ratios clearly show that efficient operation depends on picking the right jet for the right speed.
It all comes down to speed. At higher speeds, waterjets show greater efficiency. But at lower speeds, they struggle to create enough momentum change with limited water flow rates. DMS created a simple comparison, using the same waterjet for six different peak speeds. (Figure 4‑1)
In practical terms, this would be the same waterjet used on six different types of vessels. The peak speed of 60 knots represents a sleek, light patrol vessel designed to cut through the waves. The peak of 10 knots applied to a slow lumbering barge, pushing a heavy load. It was more instructive to assume a constant power and vary the peak vessel speed, because waterjet efficiency hinged on speed.
The graph showed how waterjet efficiency dropped drastically at lower speeds. Above 30 knots, waterjets offered a better option to open water propellers. Below 20 knots, propellers were the clear winner. The range of 20 – 30 knots remained uncertain. Propellers have a few tricks to remain competitive in this range, and waterjet efficiency hinges on selecting the right model. Either option has merits, depending on your circumstances.
The speed range of 20 – 30 knots is also a very popular set of design speeds for many vessels. Picking the wrong propulsor may drastically alter your fuel consumption for these applications. DMS offers careful review and comparison of propulsion options in this range.
Remember to consider your operational profile when selecting the propulsor. Notice that the waterjet efficiency drops off with speed. Don’t select a waterjet due to its efficiency at high speed if you spend 90% of the time trawling. DMS can work with you to balance all the operational needs and maximize your propulsive efficiency.
Sometimes we accept the lower efficiency of waterjets due to their massive benefits in maneuvering. Unlike conventional propellers, maneuvering works by controlling the direction of your waterjet thrust. Your steering force links to engine RPMs, not ship speed. Imagine slowly drifting up to a dock with full steering control, something a rudder will not achieve.
Reverse thrust on waterjets also promises greater control. On a conventional propeller, we reverse thrust by slowing the engine RPM, switching to reverse gear, and revving up again. On a waterjet, just drop the bucket. (see Figure 5‑1(b)) The bucket swings over the outlet of the waterjet and redirects the thrust into reverse. No need to reverse gear or change engine RPM. This offers extremely quick reaction time for crash stops.
Some waterjets include a neutral thrust position. The reversing bucket partially covers the outlet, sending half the stream in reverse and half in forward. Engine RPM’s are no longer tied to thrust. You gain the option to keep your engine at full speed for strong thrust control and only use a fraction of that when approaching the dock. Just leave the bucket in neutral. Then adjust the bucket slightly to nudge the ship. These extra options allow very fine vessel maneuvering in a range of situations.
Waterjets are fun. They give you great maneuvering control and promise much higher efficiency at high speeds. But that flexibility comes with the price of more subtle limits on performance. Efficiency rapidly drops off if you install the wrong waterjet or use it at the wrong ship speed. Used incorrectly, waterjets perform worse than propellers. The critical speeds of 20 – 30 knots are the transition from propellers to waterjets. DMS can help you decide on the right option. Achieve all the promises of waterjets without sacrificing efficiency.
For more information, please visit Underwater thruster manufacturer.