Can You See Fish With Thermal Imaging?
TL;DR
Thermal imaging usually cannot see fish clearly underwater because water blocks and absorbs much of the infrared radiation that thermal cameras detect. A thermal camera may show temperature differences on the water surface, warm objects above the surface, people, boats, animals, shoreline structure, or freshly disturbed water, but it generally will not show fish swimming below the surface the way sonar or an underwater camera can.
- Thermal can detect heat at the surface, not through deep water.
- Fish below the surface are usually not visible with a handheld thermal camera.
- Thermal can still help around water for safety, shoreline scanning, locating people or animals, and detecting warm objects.
- Sonar is the better tool for finding fish below the surface.
- Night vision can help with navigation and visible-light observation near water, but it also does not see through water like sonar.
Why Thermal Cameras Usually Cannot See Fish Underwater
Thermal cameras detect infrared radiation. They are excellent at showing heat differences on land, in the air, and on exposed surfaces. Water behaves differently. It absorbs infrared radiation strongly, which prevents the thermal signal from objects below the surface from reaching the camera in a useful way.
That means a fish swimming below the surface is usually hidden from a thermal camera, even if the fish is warmer or cooler than the surrounding water. The thermal camera is mostly reading the surface temperature of the water, not the fish underneath it.
Thermal imaging is a surface-reading technology around water. It can show what is on or above the surface much better than what is below it.
What Thermal Imaging Can Show Around Water
Even though thermal imaging is not a fish finder, it can still be useful around lakes, rivers, ponds, docks, boats, and shorelines. The key is understanding what the device can realistically detect.
| Object or Condition | Can Thermal See It? | Why |
|---|---|---|
| Fish swimming below the surface | Usually no | Water blocks most infrared radiation from the fish. |
| Fish at or breaking the surface | Sometimes | A surface disturbance or exposed body may create a temporary temperature contrast. |
| People in or near the water | Yes, often | Exposed skin, clothing, boats, and shoreline objects can create strong thermal contrast. |
| Warm rocks, docks, boats, or shoreline structure | Yes | Solid surfaces radiate heat that a thermal camera can detect. |
| Water temperature differences | Sometimes | Thermal may show surface-level temperature patterns, inflows, or disturbed water. |
| Objects behind glass | Usually no | Most common glass blocks long-wave infrared used by many thermal cameras. |
Thermal Imaging vs Sonar for Fishing
If the goal is to locate fish underwater, sonar is the better tool. Sonar sends sound waves through the water and reads the returning signal. Thermal imaging reads infrared radiation and is mainly limited to surfaces when water is involved.
| Feature | Thermal Imaging | Sonar / Fish Finder |
|---|---|---|
| Primary signal | Infrared heat radiation | Sound waves |
| Works below water surface? | Not effectively for fish | Yes |
| Best use around fishing | Shoreline scanning, safety, detecting animals or people, surface heat contrast | Finding fish, depth, bottom contour, underwater structure |
| Works at night? | Yes | Yes |
Can Thermal Imaging See Through Clear Water?
Clear water may look transparent to the human eye, but that does not mean it is transparent to a thermal camera. Human vision and thermal imaging use different parts of the electromagnetic spectrum. Water can transmit visible light while still absorbing the long-wave infrared energy used by many thermal imagers.
This is why a person can look into clear shallow water and see rocks or fish, while a thermal device may mostly show the temperature of the water surface.
Can Thermal Imaging Help With Night Fishing?
Thermal imaging can help with some parts of night fishing, but not as a direct underwater fish detector. It may be useful for:
- scanning a dark shoreline before landing a boat;
- detecting people, animals, or obstacles near a dock;
- locating warm equipment, engines, or recently handled objects;
- checking shoreline movement without using visible light;
- supporting safety during night boating or bank fishing.
For identifying fish below the surface, use sonar. For navigating, observing the shore, or detecting warm objects in darkness, thermal imaging can still be valuable.
Thermal Imaging vs Night Vision Around Water
Night vision and thermal imaging solve different problems. Night vision amplifies available light, so it can help you see the shape of a shoreline, dock, boat, or visible surface. Thermal imaging detects heat, so it can help find living beings or warm objects that stand out from the background.
| Use Case | Better Tool | Reason |
|---|---|---|
| Finding fish underwater | Sonar | Sonar is designed to work below the surface. |
| Seeing shoreline shape at night | Night vision | Night vision preserves more visible scene detail. |
| Detecting a person or animal near water | Thermal imaging | Warm bodies often stand out clearly from cooler backgrounds. |
| Scanning total darkness | Thermal imaging | Thermal does not require visible light. |
What a Thermal Monocular Can Do Near Water
A handheld thermal monocular is useful when the goal is detection, not underwater imaging. It can help a user quickly scan a field, shoreline, tree line, dock area, or open bank. For hunters, landowners, boaters, and outdoor users, that detection capability can be helpful after dark.
Relevant AGM categories include:
Practical Expectations Before You Buy
If you are considering thermal imaging for fishing, set the right expectation. A thermal device is not a replacement for a fish finder. It is better thought of as an observation and safety tool. It can help you see heat contrast in the environment, but it will not reliably show fish below the water surface.
Choose thermal imaging if you need to detect warm objects, animals, people, or shoreline activity in darkness. Choose sonar if your primary goal is locating fish underwater.
FAQ
Can a thermal camera see fish underwater?
Usually no. Water absorbs much of the infrared radiation that thermal cameras detect, so fish below the surface are generally not visible.
Can thermal imaging see through water?
Thermal imaging can read surface temperature patterns, but it generally cannot see through water in the way visible light or sonar can.
Can thermal imaging help with night fishing?
Yes, but mainly for safety and observation around the water. It can help detect people, animals, shoreline objects, and warm equipment, not fish swimming below the surface.
What is better for finding fish: thermal imaging or sonar?
Sonar is better for finding fish underwater. Thermal imaging is better for detecting heat signatures above or at the surface.
Can night vision see fish underwater?
Night vision may help you see visible objects in shallow, clear water if there is enough light, but it is not designed to locate fish underwater like sonar.
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