How to Find a Good Fishing Spot in Open Waters Using Bathymetry

How to Find a Good Fishing Spot in Open Waters Using Bathymetry

I love finding new places to fish. If I could fish in a different lake every weekend, I would! I recently discovered a tool that can help me find the best fishing spots near me. Why aren’t all anglers using bathymetry maps? Now that I know how to use them, I’ve found that my fishing experiences are more successful, as well as more fun. 

I’ll briefly explain what bathymetry is, how anglers can use it to their benefit, and then walk you through my own experience of using bathymetry on a fishing trip to increase my success. 

What Is Bathymetry? 

Bathymetry is the study and mapping of ocean and lake floors, both in terms of the depth of water and the contours of the floor surface. In fact, the word “bathymetry” comes from two Greek words—bathus, which means “deep” and metron, which mean “measure”. 

Why Is This Beneficial To Anglers? 

There are two types of bathymetry, and they both have different uses for anglers. Both can be used as data to find out important information about your fishing trip and location. Studying them before, during, and after your fishing trip can set you up for fishing success! 


Personal bathymetry is your own personal stash of maps that you’ve created and recorded based on your experience of lakes and rivers. You can do this on-the-go, using apps like Fish Deeper, or other sonar-type apps. 

Your fish finder will provide real-time data of what’s happening under the water while you’re on the lake. Your personal maps (that you create every time you fish on a new lake) will give you information that can supplement the real-time information coming from your sonar device

If you fish the same lake more than once, you’ll already have personal information about the lake stored on your device. This helps you to learn the lakes that you fish on often like the back of your hand! 


Global bathymetry is generated by a service provider. They’re detailed maps that have been studied and plotted by professionals. 

You can find global bathymetry maps online. These are particularly useful for preparation of a fishing trip. You can find information about lakes you haven’t been to yet, and decide if they’re worth visiting. 

Using global bathymetric maps can help you choose a lake or river to fish at, which route to take to get there, and which spot to set up camp, in relation to where exactly on the lake you want to fish. 

Which to Use? 

Both types of bathymetry can be extremely useful to anglers. Understanding the information you’re seeing on bathymetric maps can save you time and frustration by pointing you to the most likely spots to catch. 

Global maps can be checked the day before your trip or just before you leave. Personal bathymetry maps can be accessed where you are, without data. When used together, bathymetry can be a powerful and effective tool. 

How to Interpret Bathymetry Data 

Reading a bathymetric map isn’t hard if you understand how. Here are some tips: 

  • Lines close together means steeper terrain (further apart means flatter terrain). 
  • Warmer colors (red, orange, yellow) show shallower water, while cooler colors (green, blue, violet) indicate deep water. 

Fish don’t stay in one spot all day. Learning how fish move and identifying the areas on your bathymetric map allows you to cast your line into the space they’re most likely to be at the time. 

Understanding the layout and depths of a lake can help you choose which lake to go to before you even get on the road. Knowing what kind of fish you’re targeting is helpful, because if you know where they congregate—for example, in deep waters or near islands—you know what to look for in a lake. 

If the lake is large, you can hone in a spot or spots that you want to fish. Make sure that if you’re choosing more than one spot, they’re close enough together that you can move from one to the other easily. Knowing which spots you want to fish can also help you choose the most effective route from your home to the right area of the lake, saving you time on the road and giving you more time on the water. 

How I Use Bathymetry to Find Perfect Fishing Spots 

Bathymetry can be used before you even get out onto the water. When I plan fishing trips, I start the day before with global bathymetry, and take my personal maps on the road (or boat) with me. Here’s a run-down of how I use these maps to decide on which lake to fish, which spot on the lake to choose, and to learn more about this amazing hobby. 

Planning My Trip 

Before I even leave the house, I check out global bathymetry maps of lakes nearby (or in the particular area I want to fish). 

Picking a Good Lake 

I search for “holes” on the bottom of the lake, or deep spots which could yield plenty of fish. I’ll also look for interesting contours on the lake bottom, that could be rocks or small islands. Islands or rocky pieces often have vegetation around them, which attracts fish. If I find a combination of depth and structure in various parts of a lake, I know the lake is likely to have a good amount of fish in it. 

Choosing a Good Spot 

Many fish, like bass, trout and sunfish, stay near “structure” underwater. Structure could be rocks, logs, or just an elevated piece of ground. Fish like to stay close to possible cover in case a predator fish arrives, so they can hide or escape. When I find structure and depth on bathymetry maps, I know I have a good fishable spot. 

I then search for other fishable spots nearby. Google maps is very helpful for finding out how much distance is between fishing spots. You don’t want to choose a lake for its variety of good fishing spots only to find out that the spots are so far away from each other that you’ll spend a lot of time moving from one to the next. This is another way bathymetry can help save time. 

Getting to the Lake 

Once I’ve chosen my fishing spots where there’s likely to be a good chance of catching, I map my route from my home to the lake. Knowing exactly where I want to fish on the lake helps me to find a suitable route to the specific area of the lake I need to be at. 

Some lakes are huge! It’s great to use your GPS to find your way, but you really don’t want to end up parked on one side of the lake when your specific fishing spot is on the other. 


If I haven’t fished the lake before, I’ll begin to create my own personal bathymetry maps for the lake using my fish finder and app when I’m on the water. This is ideal as it means I don’t need to revisit all of the same info if I fish the same lake again, unless I want to choose a different spot. 


Once my fishing day is done, I analyze whether or not it was successful. If it was, I can mark it as a favorite spot so I know where to come next time. If it wasn’t successful, I can analyze the data and try to figure out why it wasn’t a good day of fishing. 

It’s worth remembering that things like water temperature, air pressure, and other activity on the lake can all have an impact on how the fish bite. The bathymetric data doesn’t change overnight, so usually the reason for a bad day of fishing is an external reason. 

Figuring this out can help me be better prepared for my next fishing trip! 


My experience with bathymetric maps has changed my fishing experience. Sure, if I want to head out for a relaxed day on the water that’s not too far from home and just try my luck, I don’t need to do my research beforehand. 

But when I’m fishing with purpose and targeting a specific catch, being able to study detailed bathymetry maps helps immensely to find the best places to go fishing near me. 

Don’t think that using these takes the luck and work out of fishing! Using bathymetry simply gives you some insight into the best spots to catch certain fish and the best times to be there. 

When you hook that fish, it’s still just you, the fish, and your hard work to reel it in!

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