Under the Boat: Basic Bottom Fishing

If you learn how to read the bottom, it will help tremendously in bringing fish to the top. This article explains how to read bottoms, and what to do when you see certain types of structure.

If you learn how to read the bottom, it will help tremendously in bringing fish to the top. This article explains how to read bottoms, and what to do when you see certain types of structure.

Understanding Thermoclines, Structure, and Fish Behavior at or Near the bottom

Most of us at TOF – and indeed many of the guides and contributors to our site – fish live bait. Let's say that 70% of the contributors are live-bait people, with 20% never touching live bait, and the other 10% not caring one way or another. If you fish live bait near or on the surface, or use lures near or at the surface (popping corks on a flyrod come to mind), you think about pulls and you think about splashes. What a lot of anglers don't think about is the structure that lies just below the surface they're familiar with. What's underneath the water you see (and hear), and what happens to the temperature of the water, are two things we're going to talk about in this article.

The Topography of the Bottom

Some bottoms are just big, flat, open and fairly-lifeless deserts. They don't hold fish. If you do catch fish there, they're open-water predators that happened to be passing over that particular desert chasing bait. In our local waters, and in most waters, bait fish in particular move a lot; seasonally they change where they are and even daily schools seem able to literally disappear. You can search the same flats for a mile or more from where you just netted them and not be able to find one. Bottoms are different. Bottoms have structure.


The depth of the water isn't the only thing important; it's what the topography (or shape) of the bottom happens to be. Different shapes mean different things, and the deeper the water the cooler it becomes. The cooler the water the slower the fish respond. Surface predators tend to be much more active, and willing to move much further than their deepwater cousins.

Fishing the Bottom

Thinking about that “side view” of the water underneath your boat (or within casting or kiting distance of the shoreline, pier, or structure you're standing on) helps you to understand where fish are sitting and most likely to bite.


In this simple graphic, you can see the “side-view” we did in the last graphic shown from the top down. Whether the right side of the graphic (the deepest spot) is eighty feet or eighty, the fish are going to be attracted by that structure – not necessarily the depth. If a fish is comfortable in eight feet of water, it's the eight feet with the roughest and most structured bottom that is going to hold the fish. That's why positioning is so important; if you're twenty feet away from where the fish are they ain't gonna move to get your bait. Reposition the boat and drop the bait on them, and the bite's on!

We're in an almost magical place when it comes to fishing. Species, conditions, structure, location on the plant, salt water, fresh water, and a passionate community all add up to something you don't find everywhere. I was able to ask my friend and partner Captain David Rieumont about the procedures that he felt were most important when you want to successfully learn how to bottom fish. David has a “detective gene” in his blood, and probably did before he wore a badge for 25 long years. He takes notes, and reads a lot. He can do more research on a subject than three normal people can do and he does it in half the time. It's how he started fishing. His answers are worth learning:

  • Learn your sounder and know what you're looking at.
  • Learn how bottom fish relate to particular structure
  • Have a wide variety of baits
  • Learn how to find a large wreck, and do a search grid on top of it. Fish it consistently to learn how fish feed relative to where and how they sit on the bottom
  • Learn and observe visible surface and atmospheric clues to know that there are gamefish below

Each of these could be an article in itself, but let's look a little deeper into each of these subjects.

Using a Sounder

You can't judge a book by its cover, and you can't judge bottom purely by how much distance there is between the transducer (the component of your sonar that actually sends and receives the mean you see displayed on the screen). Learn to use your sounder so you know the difference between hard bottom and soft bottom. The thickness of the “layer” on the bottom in this image from Garmin shows hard bottom, and fish location. But seeing little fish icons doesn't make you a better angler. Understanding what you're looking at makes the equipment much more efficient. You don't always see the little fishies where there are fishies hiding.


Our Recommended Sounders


Know how to use your sounder; it tells you far more than those little fishy icons could ever show you. The hardness (or lack thereof) of the bottom is shown by the thick lighter gray band on the bottom. If bands don't show, the bottom is soft. Learn your sounder and you'll catch more fish on the bottom

How Fish Behave

The fish we often chase don't sit on the bottom, but there are far more there than you can imagine. In the wintertime, think of sheepshead and black (what we call “puppy”) drum. Along with redfish, they often hang near the bottom of residential canals in the wintertime. Even when they're eating, they eat slower and more gently in the winter. A redfish that hits the bait running in the summer might tap a bait in the winter. Fish that hang in deep holes – like grouper – tend to be very lazy, and need bait in front of their face. Spend time working the bottom and you will learn how fish act.


Take a lot of bait with you. Take live bait as well as dead frozen bait. Things like frozen sardines will attract bottom fish that wouldn't eat something dead anywhere near the surface. Pinfish are excellent bottom baits. And, remember to take some frozen shrimp and sabikis with you whenever you're going bottom fishing; a little shrimp tail and a sabiki can put two dozen baits in your well in no time.

Positioning Your Boat

Take two markers to a known wreck. Drop one at one end and the other at the opposite end. Determine the direction your boat's gonna drift based on wind and tides the moment that you start, and work a grid. Drift and bounce baits off the bottom using a fishfinder rig, and use a variety of different baits.

BOTTOM fishfinder rig

A Fishfinder rig will allow you to drift a known rig and learn the ins-and-outs of bottom fishing

Visual Clues

Bottom fish aren't driving bait to the surface, but when fish are eating there's a feel in the air that will teach you what to expect. For example, a lack of birds, or a complete lack of wind are bad signs. And, know that if there's life around, there's life around all over. One thing we always love to see is a sea turtle; if they're around that means there's a cave. The same concept applies with anything strange or unusual. This isn't as measurable as a bottom finder telling you you're on hard bottom, but the feel of the place is definitely connected to what's under the boat. If you've ever fished the Islamorada hump (or any humps) you know what we mean. Simply approach the underwater mountain and the feel in the air changes.

Spending Time on the Water

Like anything else, we can tell you the short-story of improving the chances you will catch fish on the bottom, and what Captain David tells us works as much in inside residential canals as it does in eighty feet of water. So try his basics and find a close or nearshore (or inshore) structure in more than eight feet of water and tell us what happens.

The article below may interest you also.

Looking Up - Fish That Feed On the Bottom


Tight lines!

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