How to see Fish Underwater
Fresh water | Salt water | Flies | Tying | Casting | Gear | Fishing Reports | Places
It can be frustrating when your fishing buddy can see the fish and you can not. There are two mechanisms in human vision that create difficulty in seeing sub-surface fish. But don’t fret; this can be overcome with some cool equipment, and a bit of practice.
Human vision principle number one: We ‘see’ the brightest object in our environment, and can not ’see’ the dimmer objects.
This produces great difficulty when trying to see below the surface of water. We see the glare off the surface and nothing else. However, there may be fish underneath, invisible because of the dim subsurface light. The glare from the surface is brighter, much brighter.
This graphic shows the problem. The light from the glare of the surface (solid line) is much brighter than the light from the fish below the surface of the water(broken line.). The eye adjusts for this bright light, limiting what can be seen. In this case, the surface glare is all that we will ‘see,’ even though the light bouncing from the fish is reaching the eye. We ‘see’ the brighter portion of the image. But this can be overcome with a popular piece of gear.
Polarized sunglasses are the most important piece of gear to see subsurface fish. And specifically they must be polarized---These lenses reduce the amount of glare from the surface of the water. It is almost like magic, opening the curtains when someone puts on a pair for the first time. The light that reflects from the surface is polarized. The sunglasses have a polarized-light-filter that removes 90% of this glare. Now the brightest light is the subsurface light because it is Non-polarized. So the filters have little effect on sub-surface light. The world below the surface is now brightest, and what we ’see.’ In the above graphic, with polarized sunglasses, only the dotted line reaches the eye.
Human vision principle number two: We naturally ‘focus’ on the brightest object in our environment, and dimmer objects are out of focus.
So even when we remove the bright glaring light of the surface, we have to over come our natural focusing mechanism. Slip on a pair of top-quality polarized sunglasses, and the surface glare is gone, but our eyes are still ‘focused’ on the surface. Other objects are out of focus, hiding at different distances below the surface. It is like aiming an autofocus camera at a field of flowers. If you study the photo, you will find that only a few of the flowers are in focus, the rest are either too close, or too far to be in focus. Our eye has the same issue when seeing under water. We are accustomed to focusing on the surface, but we need to focus beneath the surface.
Above shows the second principle to overcome. The eye naturally focuses at point A. The fish may be directly in the line of sight, but the eye needs to focus at point B to see the fish. We can train our eyes to focus at different distances. It takes a little practice. One way to train the eye is to put your rod tip below the surface. Focus your eyes on the tip. Move the tip to the bottom, keep focusing on the tip, and suddenly the entire bottom is in focus. Or try thissecond tip: Cast your sinking lure or fly. Focus on it, below the surface, now you are focusing subsurface. You can train your eyes to do this without the fly in the water with a little practice. This will pay huge dividends in seeing subsurface fish. Use the rod tip trick, and the sinking fly trick to practice.
These techniques work when fly fishing for redfish and bonefish. On a recent trip to the mountains for rainbow trout, it was equally effective. Focusing below the surface is more difficult when fishing in tannic stained water, but it can be done!
Overcome the natural tendency to focus on the surface, and use a pair of polarized sunglasses on your next sight fishing trip. There is a lot to see below the surface.
Comments are encouraged and appreciated!