You’ve probably heard anglers talking about thermal scopes and wondered if they’re the secret weapon for finding fish. The short answer? Not quite the way you’d think. Fish are cold-blooded creatures whose temperature is not constant and depends on the water temperature, which makes them really hard to spot with thermal technology. But that doesn’t mean thermal scopes are useless for fishing—you just need to know what they can and can’t do.
We’re going to walk you through how thermal imaging actually works around water, why you won’t see fish swimming below the surface, and the surprising ways thermal scopes can still help you catch more fish. If you’re interested in exploring different thermal imaging options, check out our range of outdoor thermal devices designed for various applications.
Why Thermal Scopes Can’t See Fish Underwater
Here’s the deal: water absorbs infrared radiation, which reduces the effectiveness of thermal imaging, and infrared radiation does not penetrate water well. Think of water as a thick blanket that blocks the heat signatures thermal scopes need to create an image.
But there’s another problem. A thermal imaging camera displays a contrasting temperature background of the objects you are observing, and it will not show fish with the same body temperature as the water. Most fish sit at roughly the same temperature as their surroundings, so even if the infrared radiation could get through the water (which it can’t), there’d be almost no temperature difference to detect.
The primary limitation of thermal imaging underwater is the poor penetration of infrared radiation, and thermal cameras are limited to detecting heat on or very near the surface. Sound familiar if you’ve ever tried using one near a lake or river? That’s why.
What Thermal Scopes Can Actually Detect on Water
Before you write off thermal imaging for fishing completely, there’s good news. Schools of fish change the characteristics of the water’s surface, and that’s what you can see with thermal imaging. When fish are active near the surface—feeding, breaking, or moving in large schools—they create tiny temperature changes and disturbances that show up on a thermal scope.
Thermal-imaging cameras are sensitive enough to see temperature breaks — areas that tend to attract schools of baitfish and predators, as long as the water temperature changes rapidly within a few meters. This works particularly well in saltwater where you’re looking for temperature gradients offshore, or at night when you’re trying to spot baitfish dimpling the surface.
For those serious about nighttime observation and fishing applications, our Pegasus 2 LRF offers long-range detection capabilities that work well in low-light marine conditions.
How Temperature Differences Help You Find Fish
Thermal cameras can register a temperature anomaly as small as a tenth of a degree, and that difference becomes more pronounced offshore when the camera’s field of view fills with mostly water and sky. This is where thermal imaging really shines for fishing.
You can spot weed lines, kelp paddies, and floating debris that hold fish—even in complete darkness. These objects absorb heat differently than open water, making them stand out like beacons on your thermal display. Anglers say they’ve hooked tuna after finding breaking fish before daylight by using a thermal-imaging camera, and can spot schools of baitfish dimpling the surface in the dark.
While infrared radiation is absorbed by water, it is possible to detect temperature differences on the water’s surface, and fish swimming close to the surface can create disturbances and thermal anomalies. Look, it’s not x-ray vision, but it beats staring into pitch darkness hoping to stumble onto fish.
Better Uses for Thermal Scopes While Fishing
Honestly, thermal imaging does way more for fishing safety and navigation than direct fish finding. Thermal cameras cannot see through water, but they’re still the best tool for professional and recreational marine use when you need to see in total darkness.
Infrared thermal imaging cameras can reliably deliver clear thermal images even in extremely low-visibility conditions such as nighttime, heavy fog, rain, or snow, and provide all-weather identification of key targets including other vessels, buoys, shorelines, and floating debris. You’ll avoid hitting debris, spot other boats, and navigate safely—which matters more than finding fish when you’re miles offshore in the dark.
During winter fishing, thermal imaging can identify weak spots in ice, cracks, and thin areas that could be dangerous. It’s a safety tool first, fishing aid second. Our thermal monocular technology article explains more about how these devices work if you’re curious about the technical side.
Alternatives That Actually Work for Finding Fish
Sonar technology, which uses sound waves to detect objects underwater, is widely used for fish finding and can penetrate water effectively and provide detailed information about the location, size, and movement of fish schools. If you want to see what’s actually below your boat, sonar is your answer—not thermal.
Underwater cameras, often coupled with lighting systems, can capture visual images of fish and other marine life and are commonly used in marine biology, underwater research, and recreational diving. These give you actual video of what’s down there, which is pretty cool if you’re trying to figure out what fish are doing around your bait.
Thermal scopes work great for spotting surface activity and navigating at night, but they’re not replacements for traditional fish finders. Use them together and you’ll have a much better setup than relying on just one technology.
Conclusion
So can you see fish with a thermal scope? Not underwater—physics just doesn’t work that way. Water blocks infrared radiation and fish match the water temperature too closely to show up as heat signatures. But thermal scopes aren’t worthless for fishing. They’ll help you spot surface activity, temperature breaks, floating structure, and navigate safely in conditions where regular vision fails.
The best approach? Use thermal imaging for what it does well—surface observation, safety, and navigation—and stick with sonar for finding fish below the surface. Thermal technology has its place in your fishing toolkit, just not as an underwater fish camera. If you’re ready to explore thermal imaging for your outdoor adventures, visit our main product page to see our full lineup of thermal devices.
FAQs
Can thermal scopes see through water to detect fish?
No, thermal scopes cannot see through water. Water absorbs infrared radiation that thermal imaging relies on, blocking heat signatures from penetrating more than a few millimeters below the surface. Fish swimming underwater remain invisible to thermal technology.
What can thermal imaging actually help with when fishing?
Thermal imaging excels at detecting surface activity like baitfish schools dimpling the water, temperature breaks that attract fish, weed lines, floating debris, and other surface features. It’s also excellent for safe navigation in darkness, fog, or low-visibility conditions on the water.
Why don’t fish show up on thermal cameras?
Fish are cold-blooded animals that maintain body temperatures nearly identical to the surrounding water. Thermal cameras detect temperature differences, and since fish don’t create enough contrast against the water temperature, they remain undetectable even if water penetration wasn’t an issue.
Is thermal imaging or sonar better for finding fish?
Sonar is better for directly locating fish underwater. It uses sound waves that penetrate water effectively and can show exact fish locations, depths, and school sizes. Thermal imaging works best for surface observation and navigation, while sonar handles underwater detection.
Can you see fish breaking the surface with a thermal scope at night?
Yes, you can detect fish activity at the surface with thermal imaging. When fish break the surface, create disturbances, or move in schools near the top, they change the water surface characteristics enough to show up as thermal patterns—particularly useful for spotting feeding activity before dawn.
