Knowing how deep to set your float is a critical part of good float fishing, and if you do this well you will catch a lot more trout, steelhead, and salmon in the rivers that you fish. The reason for this is that your float holds the bait up or suspends it, and this means your float can prevent your bait from getting deep enough.
You want to set the depth of your float so that the bait is 8 to 16 inches off the bottom of the river because that puts the bait right in the fish’s face. To do this you need the right float and the right bait, and then you need to know how to read the float.
But how do you know how deep to set your float?
In this article, I will answer this important question so you will know how deep to set your float in any river and in each spot that you fish.
How To Know How Deep To Set Your Float
As a guide, I set or adjust my client’s floats for them because I know exactly how deep each spot is and then I watch it like a hawk to be sure I set it properly.
But many anglers don’t know how deep the spot they are fishing is and they often guess and then end up fishing too high or too low, and they don’t make the necessary adjustments to their float to get it down to the fish.
I know that presenting your bait too high or too low means they are missing fish.
Setting your float too deep from the start might mean you will be snagging on the bottom, and you may lose your hook and bait on the first few casts, therefore I tend to start shallower. The other problem is that few fish will actually feed down, so a bait that is below them won’t work well.
A recent study indicated that fish like trout, in a river tend only to feed downwards about 13% of the time. The other 87% of the time those fish are feeding on food that is straight at eye level or just above the or beside them. This is another reason why you need to set your float at about 8 to 16 inches off the bottom.
Setting it too high means your float might be too far out of the strike zone for them to see it.
Know How Deep To Set Your Float By Finding The Bottom
I tell my clients that when they get to a new spot and they can’t see the bottom or can’t visually determine the depth of the spot, their first or primary goal is to find the bottom. Once they find the bottom then they can start concentrating on catching a fish.
If they are lucky, they will catch fish while they are trying to find the bottom.
I use a few methods for finding the bottom because finding the bottom is actually harder than you think for a few reasons which I will discuss below.
Finding the bottom allows you to set your float for the right depth of the spot or the line that you are about to drift your float down. Once your find the bottom you simply make your leader below the float shorter by 6 to 12 inches.
The River Bottom Is Not Always Flat
Before I get into how to find the bottom, I need to be sure that you understand river bottoms the way I do.
One of the reasons that finding the bottom is difficult for many anglers is that the river bottom of a spot where you are fishing might not be the same depth everywhere throughout the entire spot.
The top of the pool could be deeper or shallower than the bottom of the pool, or the far bank could be deeper or shallower than the close bank, or maybe there are some high spots or some deep spots as seen in the below diagram. I will discuss how to figure all of this out.
If you are in a spot that is mostly 5 feet deep and you set your float so your bait is 1 foot off the bottom, you will catch some fish in that area, but there could be a spot in the middle, or near the back of the pool that has a 6 foot wide by 10 foot long deep trench that is 9 feet deep and that could be where 80% of the fish in that pool are holding.
This means that if you set your float 1 foot off the bottom in 5 feet of water, your bait could be 4 feet out of the strike zone for 80% of the fish in that pool.
Depth changes are not always from the top of the pool to the bottom of the pool. One side of the river could also be shallower or deeper than the other side of the river, so where you set your float for one side of the river might not be good for the other half of the river.
Guide Tip: I map out the bottom of EVERY spot that I guide so that my clients don’t miss any fish, and this is one of the reasons why some years my clients will hook over 500 fall steelhead and why we catch fish when others don’t in the same spots. Knowing the bottom really helps.
My clients will often see me change the float depth 2 or 3 times in the same spot and I do this because I want to make sure that I get their bait in the strike zone of fish that are sitting in holes or trenches that I know are deeper.
Use The Right Float Type
Using the right float and knowing what size of float to use is CRITICAL for finding the bottom and when fishing.
In a nutshell, how I find the bottom is by watching my float, or what I call reading my float. If the float keeps tilting hard downriver or is twitching and bouncing, you are likely hitting or dragging the bottom. I will get into this in more detail below.
To read the float well, you always want to use a float that is designed for river fishing and one that has a pointed top. The pointed top allows you to determine your float’s angle, and your float angle helps you determine where your leader and bait are.
The ideal angle for locating the bottom is straight up because a hard-tilted angle downriver or upriver could mean an elevated bait.
To do this, weight your leader with enough weights to straighten the leader but not sink the float, and then hold the float back using a method called trotting, or checking the float to keep the float tip pointing straight up.
Try to maintain this straight up verticle angle throughout the drift. Straight up and down usually means your bait is directly below your float and if you have your leader weighted properly the bait is at it’s deepest.
In the picture, the two floats on the left are not good for float fishing because when they tilt it’s hard to see the tilt and how much they are tilting.
All the other floats on the right side are good for float fishing, and they will be sensitive enough to be able to see any tilting and to see twitching and dragging.
I discuss my favorite floats on my page 5 Best Centerpin Floats For 2022.
Generally, the size of float that I use for steelhead, trout, and salmon, depends on the depth and the velocity of the river at the spot I’m fishing.
The exception is if you need to cast very far and need to add more weight for distance, in which case a bigger float might be required. The other exception is when locating the bottom.
If the current is too fast and it drags the leader and changes the angle from say a 90-degree straight down to an angle of 45 degrees or shallower, you will require more weights and therefore a bigger float that can handle those weights and keep your bait down.
Remember, too many weights will sink a small float, too few weights and the float will sit too high on the water and you will struggle to find the bottom.
It’s the same with the depth, shallow water requires fewer weights to get your bait down fast so a smaller float is usually good, whereas deeper water or deep and fast water will need a lot more weights and a much bigger float will be required.
As a rule of thumb, I try to use the smallest float possible when I’m actually fishing, but I will go 1 to 2 sizes up when mapping out the bottom. The float needs to be able to handle all the weights that I need to use to get my bait deep, and to cast far enough.
I might change float sizes if needed based on the depth and velocity of each spot so it’s a good idea to use a float that can be easily changed.
If you are not sure if you have too much weight, try this.
If you are in a very clear river, put on a bright bait, cast it upriver but close to your bank so when it drifts by you can see it. You want to try to see how deep your bait is and at what angle your leader is at.
If the bait is almost directly below your float and it’s deep, you are good. But if the bait is 6 feet up the river or 6 feet down the river from your float and on a sideways angle you probably need more weights, or you need to control the float speed so that it puts the bait back under the float and close to the bottom again.
If you are controlling your float speed well and you still have a more sideways angle then you need more weights and maybe a bigger float that can handle the extra weight.
Every float is different, and not all of them are right for float fishing in rivers. Whatever float you decide to use, you should know how much weight each size of that float is required to make the float sit perfectly in the water.
I discuss setting up your weights and float properly on my page Float and Weights Setup.
Use The Right Bait For Finding The Bottom
Some baits are more buoyant than others, and baits like a plastic worm that floats, or a single egg, are not good baits for finding the bottom.
Using a heavier bait like a tungsten weighted fly, or a glass bead, which are both very heavy, or even a spawn bag, are the best baits to start with to help you find the bottom.
If I start hooking fish before I hit the bottom I will keep fishing that depth because chances are it’s just above the bottom anyways. If the fish stop biting, I will often continue making my leader deeper to be sure I’m not way over their heads in other parts of the pool.
I will also purposely drag a heavy bait from the top of the pool to the bottom of the pool to be sure there is no depth change. There are times when it will drag for 20 feet and then your float will straighten. This indicates it just got deeper.
You can also use a weight closer to your bait to make it heavier and to help you locate the bottom easier.
I’ve been known to put weight 3 inches from my bait and have still caught huge weary trophy brown trout with the weight this close.
You can use my drop-shotting rig like the one in this diagram which puts your weights below the bait and gets everything deep fast.
Drop Shot Rig For Bottom Detection
The drop shot rig is my number one rig for finding and mapping out the bottom.
With the Drop Shot rig, your weight is placed at the very bottom below your bait or your fly, and the size or weight of the bait won’t matter, meaning you won’t need to use heavy baits if you don’t want to.
My bait is usually placed on a hanging tagline which can be attached with a triple Surgeons knot and leave one tag long for your bait, or use a tippet ring, or maybe a micro swivel to tie a tag and the weight dropper line.
With the Drop Shot rig, you will only add as much weight as you need to get the weight down fast without sinking your float or constantly hanging up.
The weights will gab or drag on the bottom which lets you know that you hit the bottom.
Often you will lose some weights if it gets snagged up badly, but the bonus is that you also lose almost no hooks, flies, or baits. And since weights are usually cheaper and easier to replace I prefer to lose weights.
The reason this drop shot method works better, is that with lighter baits and with traditional leader setups, the bait will simply drift or lightly drag across the bottom making which makes it very hard to detect the bottom with your float.
Since the heavy weights are at the bottom of the drop shot rig, your float will often twitch, bounce, or keep tilting hard downriver more aggressively which indicates that the weight is hitting the bottom or is hanging up.
Once you detect the bottom and determined the depth, you can continue to fish with this rig by simply shortening the leader.
However, I mostly use this method just to map out the river bottom and to determine depths throughout the entire spot. Once the bottom in mapped out, I then switch to a more productive leader setup. I discuss mapping out the bottom below.
If you going to continue fishing with this method, or a fishing and mapping the bottom at the same time, the length of line between your bottom weights and where your tag line or fly attaches can be anywhere from 6 to 24 inches.
If the fish are hugging the bottom, I will often go with an 8 to 10 -inch shot line/weight line, and a 4-inch tag line for the bait. This should keep the bait about 6 inches off the bottom and right in their face.
In winter or colder conditions or when fish are inactive, I tend to fish closer to the bottom, with the belief that the closer you can get a bait the more likely they will eat it.
In warmer or ideal water temps or when fish are moving and are active, I will try to fish my bait higher. I will also most often (if legal to do so) I will use a two-bait rig with the baits spread out 12 to 30 inches apart and both on tag lines.
If the fish are active and willing to move farther, I will use a longer 12 to 16-inch shot/weight line, and a 4 to 6-inch tag bait line.
The bait tag line, also known as the dropper line, that I have found to work the best is about 4 to 6 inches long and made from 8lb to 10lb fluorocarbon leader. Bait tag lines any longer than 6 inches tend to tangle more often or will go too deep and then drag the bottom.
For more on the best float fishing leaders for shallow, deep, fast, and slow water, see my page 5 Best Float Fishing Leader Setups.
Mapping Out The Bottom – Why It’s Important
I would not be as good as a guide if I didn’t know my spots. So one day i diced not to fish and to just go out with a bunch of heavy weight under a float and find the bottom in all the regular spots I fished and guided. This was eye-opening for me.
By doing this, I was able to detect deep spots that I didn’t know were there, high spots that I just thought were the normal depth of the entire bottom, and what I call trenches.
Finding these holes, trenches and high spots enable me to set my depth far more accurately and that accounted for almost double the fish I would normally catch out of a spot. It made me realize that I, and likely most other anglers were missing fish!
An added bonus to mapping out the bottom and knowing where these shallow and deep spots are is that there are times of the year or even times of the day when fish will hold in these deeper spots. During high sun and in the winter these holes are where I would catch 90% of the fish, but only after I figured out where the holes are.
What I discovered is that most guys make a drift, hit a 3 foot high spot, set their float accordingly, and fish the rest of the pool based on that high spot. The miss fish sitting in a 8 or 9 foot hole or trench.
And sometimes that high spot is a giant 4 foot by 4 foot bolder sitting in 7 feet of water. They tap the top of that bolder and adjust their float according, and them miss all the fish sitting on the bottom. It’s important to map out the entire pool, especially if you can’t see the bottom.
If all the fish are holding in the part of the pool that is very deep because it’s cold, or because the sun is high and bright and they don’t want to be in the shallow water, if you don’t know where that deep spot is you will end up missing a lot of fish.
In the picture above I show you an exact river bottom map of a favorite steelhead pool on my guiding run.
During low light hours or when the fish are moving in early fall, I will catch almost all my steelhead at the top of the pool near the rapids which is where they will stop for a couple minutes to rest before they shoot up through the rapids to the next pool. This is a great spot early morning and just before dark when they are ready to start moving up the river.
During mid-day when the sun is high and the fish stop moving and they are less active I stop catching fish at the top of the pool and I will catch them all in the middle of the pool where the current is slower.
In late fall or wintertime when the water is ice cold, I only catch fish in the deepest part of the pool where they are holding. This is why mapping this one particular pool has put hundreds of steelhead on the line for my clients. On that same stretch of river, I have many other pools that go from shallow to deep or have trenched that the fish tuck into.
An angler that doesn’t have this pool mapped out and doesn’t know there are shallow and deep spots will hit bottom in the middle of the pool where it is shallowest and then set their float at 3 to 4 feet deep and that means they will miss all those fish sitting 9 feet down.
I see this happen all the time, anglers bump or locate the bottom, set their float to that level, and then never touch it again, and they miss a lot of fish because of this.
Fish during the winter or fish holding in very deep water are often less active and won’t move very far for a bait which is why you need to find these deep spots and map out the bottom of the pool.
Mapping the bottom has allowed me to catch 10 times more fish, and allows me to stay on fish under all conditions and at all times of the year.
How Do You Set Your Float
The first thing to do when setting your float is to look at the spot you are about to fish and try to determine how deep it is by what you can see.
If you can’t see the bottom just guess based on what you can see.
At the edge of the bank, you might be able to see the bottom out into the river until it looks to be about 3 feet deep and then you lose sight of the bottom. Maybe you can see the bottom at 4 or 5 feet deep before you lose sight of the bottom. This is the depth that I would start with.
If I lose sight of the bottom at 3 feet deep I set my float to 3 feet deep and make a cast in close and see if I either hook a fish or a hook bottom. If nothing happens I make it 1 foot deeper and cast into the same spot and see what happens.
I also use just the angle of my float to help detect the bottom because sometimes you will be on the bottom but the float won’t pull under. When searching for the bottom I will hold the float back just enough so that it stands perfectly straight up, if it keeps hard tilting downriver I’m hitting or dragging the bottom.
If I don’t hit bottom on my first couple of drifts, I will keep making my float deeper until I start hitting the bottom. Once I hit bottom I will make my leader 6 to 12 inches shallower or shorter because I know fish feed up and I will make a couple of casts and hope for a fish.
Then I will move my float out 1-foot further and see what happens in that line. If I don’t hit the bottom there, I will make it 1 foot deeper and I will repeat until I hit the bottom there and then move it one foot further again and repeat the process.
I will repeat this method all the way across the entire spot because it might be 4 feet deep at 10 feet out from the edge of the bank that you are standing on, but it might be 8 feet deep 15 feet further out.
I fish or drift my float in lines from the top of the pool to the bottom of the pool and I find the bottom with every line until I know where the bottom is. This is how I map out the bottom of the pool.
Once I have mapped out the bottom of the river, I memorize it so I know how deep I need to be each and every time I fish that same spot.
The key is, once you start hitting the bottom, shorten up your leader by 12 inches so you are not dragging the bottom.
When I move to the next spot I repeat the process.
If you want to know how I teach my clients to fish in lines or how to cover the water effectively, I suggest reading my article Effectively Covering The Water When Float Fishing.
How Do You Find The Holes?
Finding the holes can be difficult but it’s not impossible.
I talked about dragging a heavy bait or some weights across the bottom to locate the bottom. Once I find the bottom I will make my leader 12 inches shallower and make a couple of good clean drifts at the right depth. Good clean drift means having the proper angle and speed.
Speed control is the most critical fundamental of good float fishing and you can see more about that on my page Controlling Your Speed For More Fish When Float Fishing.
To find out if there is a hole or trench, after a couple of good drifts and before I move my cast 1 foot further out I will make it deeper by 1 or 2 feet and purposely try to drag the bottom while trying to hold my float as straight up and vertical as possible.
What I’m looking for is, if the float keeps wanting to hard tilt downriver but then all of a sudden stands straight up and doesn’t want to hard tilt downriver, it likely means it just got deeper in that area, and that means I just found a hole. Remember where this hole is by using markers along the bank, or in the water.
I will sometimes line the top of the hole up to a rock, or tree stump to help me remember the hole when I return.
Sometimes a hole or trench on the bottom might only be a small 8-foot by 3-foot trench that is 3 or 4 feet deeper than the rest of the pool and many fish will hold there.
Sometimes, the pool could be shallow at the top but then deeper near the back of the pool. If you are hitting lots of bottom in the first 30 feet and set your float at 3 feet to fish that first 30 feet but the back half of the pool is 9 feet deep you will miss a lot of fish at the back of the pool.
Once I find a hole I will remember exactly where my float went from tilted downriver to standing up because that is the start of the hole and I will make repeated casts right where the hole starts and will make it deeper and deeper until I hit the bottom of that hole.
I will also remember where the float starts to drag again because that is the end of the hole. The hole might be 5 feet long or 35 feet long.
I repeat all these steps and drag the bottom from one bank to the other and from the top of the pool to the bottom of the pool until I have completely mapped out this pool, and then I move to the next one and do it again.
Fishing Holes, Trenches, and Multiple Depth River Bottoms
I mentioned earlier that I set the float depth for my clients, and that often I will change that depth multiple times throughout the same spot. I do this to be sure my client’s bait is deep enough in all parts of the spot we are fishing.
This means I will often fish a spot like it is 2, 3, or 4 spots in one, and I will have them fish each section separately and at different depths based on my knowledge of mapping out the pool and how deep it is and where the holes and high spots are.
Doing so is the reason why I can watch guys fish a whole before us and while they catch few fish, and once they leave we can go in a catch a lot. It’s simply because they don’t know the bottom, the holes, and where the fish hold. And also, because most guys fish the same leader length through out the entire spot.
Fundamentals Of Float Fishing
Controlling your depth during the presentation is only one of the 4 fundamentals of float fishing that I teach when guiding. Sure, being good at setting your depth will help, but only if you also do the other 3 fundamentals well.
It’s important to know and do all 4 fundamentals well if you really want to catch more fish when float fishing. If you are not sure what these 4 fundamentals are, check out my page Centerpin Fishing For Beginners: 20 Steps From A Top Guide.
Also, if you know someone that struggles to catch fish when float fishing, be a good friend and share this website with them too.
Got A Question About How Deep To Set Your Float
The two best methods for finding the bottom are to use the drop shot rig or use the drag method with a heavy bait or fly. But if you have a question, comment, or tip regarding how deep to set your float let me and other readers know in the comments section below.