Underwater drones do not fly, and that changes almost everything about how you shop for one. A tethered ROV like the Chasing M2 Pro, the QYSEA FIFISH V6 Expert or the BlueROV2 sits below the surface on a cable, runs off a battery pack or a surface power supply, and sends live video up to a laptop or a phone on the boat. There is no flight time in the aviation sense, no airspace class, and no chance of a flyaway. Instead you care about depth rating in meters, run time in minutes, camera sensor size, tether length and how easy the thing is to repair when salt water eventually wins. If you want something that flies, start with our best drones for beginners guide instead.
Here is the regulatory wrinkle most buyers miss. The FAA’s drone rules cover aircraft operating in the national airspace, so a submersible ROV is not a registered aircraft and Part 107 does not apply to it. The moment you add an aerial drone to the same job, though, the rules snap back into place: any flying drone over 250 grams needs registration and Remote ID, and commercial work needs a Part 107 certificate. Canadian operators live with a similar split under Transport Canada’s drone safety rules. Our drone laws in the USA and drone laws in Canada breakdowns cover the flying side in detail.
We compared these machines the way a working operator would. Depth rating comes first, because a 100 m hull and a 300 m hull are different products with different seals and different service intervals. Then run time under load, not the marketing number: a Chasing M2 Pro running its thrusters hard drains faster than the box suggests. Camera specs matter more than people expect, since a 1/2.3 inch sensor behind murky water needs light and honest color science. We also weighed tether management, thruster layout, spare part availability and how much of the software is locked down. Every pick below has a real weakness, and we name it.
Prices shift constantly, so we do not quote them. Use the check price links, and browse the best drone accessories page for the extras that actually matter underwater: a spare battery, a tether reel, a floating lanyard and a hard case. Battery care is its own discipline here, because a lithium pack that spends winter at full charge in a hot garage dies early. Our drone battery care guide applies almost word for word to ROV packs. Fishing and hull inspection are the two fastest growing uses, and we cover the surface side in our best fishing drones roundup.
How Do the Top Options Compare?
| Underwater Drone | Best For | Max Depth | Run Time | Camera | Price |
|---|---|---|---|---|---|
| Chasing M2 Pro | Best overall for most buyers | 150 m (200 m option) | Up to ~4 hrs light use | 4K 30fps, 1/2.3 inch CMOS, 12 MP | Check price |
| QYSEA FIFISH V6 Expert | Best 360 degree maneuverability | 150 m | Up to ~4 hrs with dual battery | 4K 30fps, 1/2.3 inch CMOS, 12 MP | Check price |
| BlueROV2 / BlueROV2 Heavy | Best open source platform | 100 m standard, 300 m Heavy | 3 to 4 hrs on 18 Ah pack | 1080p low-light HD (no 4K stock) | Check price |
| Chasing Gladius Mini S | Best lightweight travel pick | 100 m | About 2 hrs | 4K 30fps, 1/2.3 inch CMOS, 12 MP | Check price |
| QYSEA FIFISH E-GO | Best entry level ROV | 100 m | About 2 hrs | 4K, 1/2.3 inch CMOS | Check price |
Depth ratings, run times and sensor specs come from manufacturer documentation and assume a fully charged pack, calm water and the standard tether. Optional depth upgrades, extra batteries and payload modules change every figure above. Check current pricing at the links in the table, since it moves constantly and we do not list dollar amounts.
1. Chasing M2 Pro , Best Overall Underwater Drone for Most Buyers
Chasing built the M2 Pro for people who need one machine to do several jobs. It carries eight vectored thrusters, two more than the QYSEA V6 Expert, and that extra pair shows up in moving water where the hull holds its heading instead of sliding sideways. The depth rating is 150 m out of the box with a factory option to push deeper, and the standard tether runs 200 m. Weight lands around 4.5 kg in air, so one person can lift it off a dock without help.
The camera is a 1/2.3 inch CMOS sensor shooting 12 MP stills and 4K video at 30 fps, with 1080p at higher frame rates when you want smoother motion. Chasing rates the battery at roughly four hours in light use, and that number is honest if you are drifting and filming. Run the thrusters flat out against a tide and you will see closer to two and a half hours. Add the 6,000 lumen lights and drain climbs again.
What won us over is the accessory line. A grabber claw, a sonar module, a laser scaler for measuring hull defects and a towable buoy all mount without adapters. Repairs are straightforward because Chasing sells individual thrusters and motors. The catch is tether drag on a long run, plus an app that gets sluggish when you push 4K video, sonar and lights at once. Check the Chasing M2 Pro on Amazon
Key strengths:
- ✅ Eight vectored thrusters hold position in current better than six-thruster rivals
- ✅ 150 m depth rating with a 200 m tether in the standard kit
- ✅ Accessory line covers claw, sonar, laser scaling and extra lighting without adapters
- ✅ Individual thrusters and motors sold separately, so repairs beat replacing the whole unit
- ✅ Roughly four hours of light-use run time from one battery pack
- ❌ Around 4.5 kg in air makes it a two-hand carry once the tether reel is attached
- ❌ App frame rate drops when you run 4K video, sonar and lights together
- ❌ Battery life falls to about two and a half hours under hard thruster use
Who it’s for: Buy the M2 Pro if you want one ROV that handles hull inspection, search and recovery, and weekend filming without learning a build.
2. QYSEA FIFISH V6 Expert , Best for 360 Degree Maneuverability and Pro Inspections
QYSEA’s pitch with the V6 Expert is posture. Six thrusters in a full omni-directional layout let the hull rotate on any axis and hold an angle while it travels, which is exactly what you want when you are filming a propeller shaft from six inches away. Depth rating is 150 m, and the camera is a 1/2.3 inch CMOS sensor with a 166 degree field of view, 12 MP stills and 4K at 30 fps.
The dual battery setup is the practical win. Two packs give up to four hours of claimed run time and let you swap one while the other keeps the ROV alive, which matters on a paid inspection where downtime costs money. Weight sits just over 4 kg. The Q-Interface software runs on a phone, tablet or VR headset, so the same unit works for a solo diver and a two-person survey crew.
Add-ons cover a robotic claw, a 200 m tether, a 6,000 lumen light set, sonar and a positioning system for repeatable transects. The honest downsides: the tether is thinner and less forgiving of abrasion than Chasing’s, replacement parts ship through a smaller dealer network, and the app wants a fairly recent phone. The 360 degree control also takes a session or two to learn, and holding a fixed roll angle is genuinely disorienting at first. Check the QYSEA FIFISH V6 Expert on Amazon
Key strengths:
- ✅ Full 360 degree omni-directional movement, including lateral and rotational holds
- ✅ Dual battery design supports hot swaps and up to four hours of claimed run time
- ✅ 166 degree field of view on a 1/2.3 inch 12 MP sensor reaches into tight spaces
- ✅ Q-Interface app runs on phone, tablet and VR headset
- ✅ 150 m depth rating matches the Chasing M2 Pro
- ❌ Thinner tether is more prone to abrasion damage on rough structures
- ❌ Smaller dealer network means longer waits for spare parts
- ❌ 360 degree control has a learning curve that frustrates first-time pilots
Who it’s for: Pick the V6 Expert if your work involves hovering in one spot at odd angles, such as hull surveys, tank inspections and propeller checks.
3. BlueROV2 / BlueROV2 Heavy , Best Open Source Option for Researchers and Builders
The BlueROV2 is the odd one out because it is not a finished consumer product. Blue Robotics sells it as a partly assembled, fully open platform running ArduSub on a Pixhawk flight controller and a Raspberry Pi companion computer. The standard hull is rated to 100 m. The Heavy configuration swaps in a larger frame, eight thrusters and a 300 m depth rating. Weight in air is around 11 kg depending on battery and ballast.
You give up camera polish to get that flexibility. The stock camera is a 1080p low-light HD unit, not 4K, and the footage looks flatter than what Chasing or QYSEA produce out of the box. An 18 Ah 14.8 V pack runs roughly three to four hours depending on how hard you push the thrusters, and the standard tether is the known weak point that most owners upgrade first.
Where it wins is control. You can write Python scripts that talk to the ROV over MAVLink, log sensor data, and add a DVL, a gripper, a manipulator arm or a custom payload bay. Spare parts are cheap and usually in stock. The tradeoff is time, because you will spend evenings tuning parameters a Chasing owner never sees. It is also awkward to launch from a small boat, and the open frame catches fishing line and weed. Check the BlueROV2 on Amazon
Key strengths:
- ✅ Fully open source hardware and software, with ArduSub on Pixhawk plus a Raspberry Pi
- ✅ 100 m standard depth rating, 300 m in the Heavy configuration
- ✅ Cheap, in-stock spare parts and documented repair guides for every module
- ✅ Scriptable over MAVLink for custom payloads, sensors and autonomous missions
- ✅ Three to four hours of run time from an 18 Ah battery pack
- ❌ Stock camera is 1080p, so footage looks flat next to 4K rivals
- ❌ Around 11 kg in air makes launching from a small boat awkward
- ❌ Setup and parameter tuning takes real time before the first serious dive
Who it’s for: Choose the BlueROV2 if you are a researcher, university team or builder who values open firmware and repairability over out-of-the-box polish.
4. Chasing Gladius Mini S , Best Lightweight Pick for Travel and Casual Dives
The Gladius Mini S exists for people who want to throw an ROV in a backpack and forget about it until the weekend. It weighs 1.2 kg in air and rates to 100 m, and the camera is the same 1/2.3 inch 12 MP sensor family used across the Chasing line, shooting 4K at 30 fps. Battery life is about two hours, roughly half of the M2 Pro, and the tether runs 100 m.
You feel the size difference in current. Four thrusters instead of eight means the Mini S gets pushed around in a swell, and there is no room for the sonar or laser modules that fit the bigger hull. What it does well is quick dives: a boat ramp, a dock piling, a fast look at a mooring chain. Set it up in two minutes and hand the controller to someone who has never flown an ROV.
The port list is short by design. No grabber claw, no sonar, no expandable payload bay, and a shorter warranty than the M2 Pro. It is still the one we recommend for travel, because every other machine in this comparison needs its own case and a second pair of hands.
Key strengths:
- ✅ 1.2 kg in air, small enough for a backpack or carry-on
- ✅ 100 m depth rating and 100 m tether cover most recreational dives
- ✅ Same 4K, 1/2.3 inch, 12 MP camera family as the larger Chasing models
- ✅ Two-minute setup that you can hand to a first-time pilot
- ✅ The lowest-cost route into a 4K, 100 m rated ROV
- ❌ About two hours of run time, and less when fighting current
- ❌ Four thrusters get pushed around in swell
- ❌ No support for sonar, claw or laser modules
Who it’s for: Get the Mini S if you want a travel-friendly ROV for casual dives, dock checks and shallow filming rather than professional surveys.
5. QYSEA FIFISH E-GO , Best Entry Level Underwater Drone
The E-GO is QYSEA’s stripped-back model for hobbyists. Depth rating is 100 m, the camera is a 4K unit on a 1/2.3 inch sensor, and the whole package is light enough to carry in one hand with the tether spool. Battery life sits in the two-hour range, and the control layout keeps the same omnidirectional logic as the bigger V6 line with fewer thrusters doing the work.
It handles like a smaller, slower V6 Expert. You still get lateral movement and a tilting camera, so lining up a shot on a reef or a sunken piling is straightforward. What you lose is pace. The E-GO moves like a camera on a stick rather than a vehicle, and it struggles against any real current or surge.
Software is the same Q-Interface app, which means the same firmware updates and the same phone requirements. Accessory support is thin, and QYSEA clearly pushes buyers toward the V6 line once they want sonar or a manipulator claw. For a first ROV that lives in a car trunk and comes out on weekends, that tradeoff is fine.
Key strengths:
- ✅ Light enough for one-hand carry with the tether spool attached
- ✅ 100 m depth rating covers most recreational and dock inspection dives
- ✅ 4K video on a 1/2.3 inch sensor using the same app as the V6 line
- ✅ Omnidirectional control, so lateral movement is available at the entry tier
- ✅ Two-hour battery covers a normal session
- ❌ Slower and weaker in current than the V6 Expert
- ❌ Almost no accessory support for sonar or a manipulator claw
- ❌ Video quality drops fast in low light without extra lamps
Who it’s for: Buy the E-GO if you want a simple, portable first ROV and do not need sonar, claws or deep-water inspections.
Frequently Asked Questions
Do I need an FAA license to operate an underwater drone?
No. The FAA regulates aircraft in the national airspace, and a tethered submersible never enters it, so Part 107 and registration do not apply to the ROV itself. If you fly an aerial drone as part of the same job, that aircraft does need registration over 250 grams and a Part 107 certificate for commercial work.
How deep can these underwater drones actually go?
The Chasing M2 Pro and QYSEA FIFISH V6 Expert are both rated to 150 m, the Gladius Mini S and FIFISH E-GO to 100 m, and the BlueROV2 reaches 300 m in its Heavy configuration. Depth ratings assume clean seals and a properly maintained hull.
Which underwater drone is best for hull inspection?
The QYSEA FIFISH V6 Expert is the strongest pick for hull work because its six thrusters hold a fixed angle while filming welds and anodes. The Chasing M2 Pro is a close second and has a better accessory line for measuring defects.
Do underwater drones need a tether?
Yes, all three brands use a tether that carries power and video. Radio does not travel through water, so wireless control is not an option at these depths. Tether length, usually 100 m to 200 m, sets your practical range.
Is the BlueROV2 hard to set up?
It arrives mostly assembled, but expect a few evenings of software setup before your first serious dive. ArduSub parameters, tether connections and ballast tuning all need attention. Once configured, it runs like any other ROV.
How long do the batteries really last?
Plan on two to four hours depending on model and conditions. Chasing rates the M2 Pro at about four hours of light use, the Gladius Mini S at roughly two, and the BlueROV2 at three to four hours on an 18 Ah pack. Cold water and heavy thruster use cut those numbers.
What Should You Remember?
- Depth rating drives cost more than camera specs. A 100 m hull and a 300 m hull use different seals, different pressure testing and different margins.
- Chasing wins on accessories. The M2 Pro mounts a grabber claw, sonar, laser scaler and 6,000 lumen lights without adapters.
- QYSEA wins on movement. Six omni-directional thrusters let the FIFISH V6 Expert hold a roll angle while it travels sideways.
- BlueROV2 wins on control. Open source ArduSub firmware and in-stock spare parts beat any consumer app if you plan to modify hardware.
- Real run time is 2 to 4 hours. Cold water, current and constant thruster use cut the marketing number roughly in half.
- FAA rules do not cover submersibles. Any aerial drone you fly on the same job over 250 grams still needs registration and Remote ID.
- Battery care decides lifespan. Store ROV packs at partial charge and never leave them full in a hot garage.
This article is for general information only. Drone regulations vary by region and change frequently , always verify current local laws and airspace rules before flying.
