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How to Read Water: Understanding the Flats, Surf, Muds, Bait & Bottom

The sight fisherman's crash course to learning how to read the water, understand the bottom and track bait activity when fishing.

How to Read Water: Understanding the Flats, Surf, Muds, Bait & Bottom

A close view of the baits that make up those dark bait balls. 

Sight fishing may be the most challenging of all fishing, but the reward is stalking and successfully “feeding” a fish. But it’s not always a case of seeing a fish. It may be seeing something in or on the water that tells you a fish is there, or if an area even looks like it might produce. Anglers should learn to read the water for visual clues at times like this, both inshore and offshore. 

Shallow Tidal Flats 

Seeing bonefish, redfish or permit tail is a luxury. As is the visible form of a fish in clear water in good sunlight. It’s the more subtle signs you need to recognize. Wakes of swimming fish can be spotted at a distance, and you must understand that the fish will be located ahead of the wake it produces. That gives you an idea where to cast your fly, lure or bait. The faster a fish is swimming, the father ahead of the wake it will be. Schools of fish will sometimes create a mix of wakes, making the surface look rippled, or “nervous” as flats anglers like to say. 

Muds 

fish muds left behind by a passing bonefish
Faint fish muds can be spotted on the flats. This one was made by a bonefish that has since moved on.

Throw out the old adage that muddy water spells poor fishing. Of course, if an entire bay is muddy for miles, it’s discouraging, and you can’t get a read on much at all. Smaller areas of stirred-up water can be golden, in the case of mullet foraging for detritus and disturbing soft bottom. A mullet mud is a magnet, especially if limited in size and surrounded by clearer water. Gamefish such as red drum, snook, seatrout, snapper, and more come into the muds to prey on whatever is stirred into the water column. From the casting deck of a skiff, and certainly the poling platform, you can spot muds from quite a distance. Same goes for stingray muds, which can be a sure thing some days. A ray will flap its wings, while digging through the bottom to eat the same same goodies the fish seek. The aforementioned fish all check out mudding rays to pick off the shrimp, crabs and small fish the ray kicks up. You might not even see the fish at all in the brightest “plume” a ray creates. But any fish present will be aggressive in striking a lure or fly. 

General Depth and Bottom Makeup 

school of anchovies in the water with birds above
With good sun, juvenile bay anchovies ball up and demand your attention. Predators such as snook, mackerel and tarpon feed on them.

It is imperative to know water depth, whether for navigation consideration, or as it applies to your fishing. 

If you lack electronics (depth finders) then learn how color clues you in as far as the water’s depth. Blue, green or turquoise water is normally adequate for small to medium-sized boats. Generally the deeper these colors, the deeper the water. Deep water will contrast greatly with shallow banks in good sunlight, but on overcast days the separation is not as distinct. If the above water colors seem pale, assume it is on the shallow side. White water indicates a shallow sand bar. Throw in the dark greens or brown hue of seagrass, and it gets tougher to discern. Light brown or yellow almost always indicates a shallow and sometimes rocky bottom. Offshore, black water in sunlight can cover a coral reef close to the surface, and it is sometimes spotty, where coral heads reach for the surface. 

Wading birds are indisputable indicators of shallow water! Long-legged herons and great egrets should tell you there’s a flat up ahead. If you are stalking fish, if the birds are tip-toeing along with “lots of leg” showing, perhaps it’s too shallow for the bonefish, reds or snook you seek. 

Bait Schools 

birds fly in the sky above schools of baitfish in the water
Birds and bait can be spotted from afar and are a great sign of action.

The presence of bait can be subtle and it can be quite obvious, even to inexperienced anglers. A big autumn push of migrating mullet can be spotted a mile or more away, whether fish are attacking from below, or birds are feeding from above. The school appears darker than the surrounding water, particularly where shallower than 6 feet or so. Whatever the bait, be it silver or striped mullet or much tinier bay anchovies for example, expect the darker color, especially over sandy bottom, and always check the sky above to be sure you are not looking at a cloud shadow. Clues to fish in the midst of a bait school can be dramatic, but not necessarily so. In the Florida surf, summer is a great time to cast to cruising snook that feed between spawning sessions. They tend to be ghost white in those environs, and tough to spot in marginal light. The snook like to feed on juvenile bay anchovies.

As mentioned, the anchovy schools tend to appear dark in the water. But you can see signs that there are snook, or perhaps small tarpon or Spanish mackerel among the baits. Watch for the bait ball to change in shape suddenly, or suddenly split into two schools. That’s a sign of predators “dogging” them. If the baits suddenly come in tighter to the dry sand, it’s time to cast seaward of the school, where fish should be. Also, look for “white holes” that open up in the bait. You might even spot the predatory fish themselves. 

“Oil slicks” on the water can be spotted at quite a distance and can be indicators of baitfish such as menhaden. Also called bunker, or pogies, these calorie-rich prey are oily, and when fish attack them, the oils rise to the surface. Never pass a slick up, depending on where you fish, you might be rewarded with Spanish or king mackerel, seatrout, snook blues, jacks, false albies or tarpon.




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