Ask how deep a lake is and you will usually get one number. On a boat-ramp sign, an agency page, or a fishing map, it is likely to be the maximum depth: the deepest known point in the basin.
That number is useful. It is also easy to give too much work.
A 60-foot maximum does not mean the lake is mostly 60 feet deep. It does not tell you whether the deepest water is a broad basin or one narrow hole. It does not tell you where the thermocline sits, how far the water level has moved, or where a fish will be on Saturday morning.
Before we wrote another guide telling anglers how to use maximum depth, we wanted to know what the number looks like across a large public catalog. We froze the 37,672-water DepthScout manifest on August 17, 2026, separated the 37,234 records classified as lakes, screened the depth field, and analyzed 37,233 maximum-depth values.
The middle lake did not reach 100 feet, or even 50. Its maximum depth was 33 feet.
Maximum depth tells you how far down a lake goes. The contours tell you how the lake gets there.
What we found
- The median recorded maximum depth was 33 feet. Half of the analyzed lakes were shallower; half were deeper.
- The middle half ran from 19 to 59 feet. Those are the 25th and 75th percentiles.
- Seven in ten lakes topped out at 50 feet or less. The exact count was 26,158 of 37,233, or 70.3%.
- More than one in three topped out at 25 feet or less. That group contained 14,226 lakes, or 38.2%.
- Only 3,319 records exceeded 100 feet. That is 8.9% of the analyzed snapshot.
- Contour provenance changed the middle only slightly. The survey-backed group had a median maximum of 35 feet; the approximated-contour group had a 33-foot median.
These are descriptions of the DepthScout catalog, not universal facts about every lake on Earth. The catalog is broad, but it is not a random sample. Ontario, Sweden, Wisconsin, Minnesota, and other regions with large public inventories contribute many more records than places where reusable lake data is scarce.
Figure 1
Most catalog lakes top out between 11 and 50 feet
Analyzed lakes by recorded maximum-depth band
View figure data as a table
| Maximum depth | Lakes | Share |
|---|---|---|
| 1–10 ft | 4,343 | 11.7% |
| 11–25 ft | 9,883 | 26.5% |
| 26–50 ft | 11,932 | 32.0% |
| 51–100 ft | 7,756 | 20.8% |
| 101–250 ft | 2,813 | 7.6% |
| Over 250 ft | 506 | 1.4% |
Why the median is more useful than the average
Deep lakes stretch the upper end of the distribution. Crater Lake reaches nearly 2,000 feet. Lake Tahoe and several Norwegian lakes pass 1,000 feet. A relatively small set of basins like those can pull an arithmetic average upward even though most anglers are looking at much shallower water.
The median asks a plainer question: if every included lake were lined up from shallowest maximum to deepest maximum, what value would sit in the middle? Here, it is 33 feet.
That does not make 33 feet the depth of a “typical” lake in a biological or geological sense. A five-acre kettle pond, a broad prairie reservoir, and a narrow mountain lake can share a maximum depth while behaving nothing alike. It simply gives the center of this catalog without letting a few exceptional depths dominate the answer.
The range around that center matters just as much. One quarter of the records topped out at 19 feet or less. Another quarter went beyond 59 feet. The word lake covers a remarkable amount of underwater terrain.
Figure 2
Out of every 100 catalog lakes, about 70 stop at 50 feet
A 100-lake view of the maximum-depth distribution
- 25 ft or less14,226 lakes38.2%
- 26–50 ft11,932 lakes32.0%
- 51–100 ft7,756 lakes20.8%
- Over 100 ft3,319 lakes8.9%
View figure data as a table
| Maximum depth | Lakes | Share |
|---|---|---|
| 25 ft or less | 14,226 | 38.2% |
| 26–50 ft | 11,932 | 32.0% |
| 51–100 ft | 7,756 | 20.8% |
| Over 100 ft | 3,319 | 8.9% |
Six real maps that put the distribution in context
The median is most useful when it sends you back to actual water. These examples span the distribution and make the report's central distinction visible: maximum depth sets the scale, while contour shape and provenance decide how closely you should read it.
- Lake Winnebago, Wisconsin reaches 21 feet and uses survey-backed contours. Its broad, shallow basin makes small depth changes carry more weight.
- Lake Mendota, Wisconsin reaches 80 feet with survey-backed contours, giving anglers several distinct depth zones to compare.
- Old Hickory Lake, Tennessee reaches 60 feet. Its contours are approximated, so use the map to understand basin-scale relationships and verify small features on the water.
- Pear Lake, British Columbia reaches 15 feet. It is a useful example of a shallow map where modest relief can be meaningful, but its contours are approximated.
- Sandy Lake, British Columbia reaches 21 feet and also carries approximated contours. Treat narrow turns as questions to check, not surveyed targets.
- Mabel Lake, British Columbia reaches 658 feet. The extreme maximum changes the visual scale, but its approximated contours do not establish the precise route of every deep break.
Browse the wider Wisconsin, Tennessee, and British Columbia map collections to compare these examples with nearby waters.
Maximum depth is a ceiling, not an address
Imagine two lakes that both list a 40-foot maximum.
The first is shaped like a cereal bowl. Much of its bottom slopes steadily toward a wide, deep basin. The second is a shallow dish with a small old creek channel touching 40 feet near the dam. Their headline number matches. The water available to fish does not.
Figure 3
Same maximum depth. Two very different lakes.
A conceptual cross-section—not a surveyed basin
This is why a maximum-depth field and a bathymetric map answer different questions. NOAA defines bathymetry as the depths and shapes of underwater terrain; contour lines connect places of equal depth. The single maximum identifies the deepest recorded point. The contours show how the rest of the bottom gets there.
Mean depth is different again. A USGS lake-data definition expresses mean depth as lake volume divided by lake area. Calculating it requires more than the deepest sounding. DepthScout does not substitute maximum depth for mean depth, and this report does not attempt to estimate mean depth from a shoreline.
For map reading, the distinction is practical:
- Maximum depth sets the scale. A 20-foot lake and a 120-foot lake call for different expectations when you scan the legend.
- Contour spacing shows the route. Tight lines mark a fast depth change; wide spacing marks a gentler one.
- Shape shows how much water belongs to each depth. One isolated hole should not be treated like a lake-wide basin.
- Location makes the number fishable. A deep point beside a channel swing, point, flat, or access site is more actionable than the maximum by itself.
Most maps do not need triple-digit depth to be interesting
The 50-foot threshold is not a biological rule. We use it because it is a clean way to describe the distribution and because anglers often assume a useful contour map must contain dramatic deep water.
It does not.
A lake that tops out at 24 feet can still have sharp breaks, inside turns, submerged points, weed edges, old channels, and small depressions. In a shallow basin, a two- or four-foot change can be the meaningful change. Reading only the maximum can make modest relief look unimportant when it may organize much of the fishable structure.
Deep water creates its own complications. Wisconsin DNR notes that depth is one of several characteristics that influence thermal stratification; surface area, water source, and clarity matter too. EPA guidance describes a common summer pattern in stratified lakes in which temperature and dissolved oxygen decline with depth. That means “deeper” is not automatically “better habitat,” even when a chart shows plenty of water below the fish.
The map gives you the container. Season, weather, oxygen, light, forage, and species behavior help decide which part of that container matters today.
Survey-backed and approximated lakes have similar middle depths
DepthScout labels contour geometry as either survey-backed or approximated. In this snapshot, 14,208 analyzed lakes carried survey-backed contours and 23,025 carried approximated contours.
Their maximum-depth distributions were close in the middle:
| Displayed contours | Lakes | 25th percentile | Median | 75th percentile |
|---|---|---|---|---|
| Survey-backed | 14,208 | 20 ft | 35 ft | 60 ft |
| Approximated | 23,025 | 18 ft | 33 ft | 56 ft |
This is not evidence that modeled contours are as accurate as measured ones. It means the contour label and the maximum-depth value describe different parts of the record.
Survey-backed tells you that the shape of the displayed contours comes from measured bathymetry. Approximated tells you that DepthScout modeled the basin between a real shoreline and a sourced maximum depth. A modeled lake can still have a credible maximum-depth record; it simply does not have measured geometry for every line between shore and bottom.
Figure 4
The middle depth barely changes with the contour label
Recorded maximum-depth quartiles by displayed contour provenance
View figure data as a table
| Contour label | Lakes | 25th percentile | Median | 75th percentile |
|---|---|---|---|---|
| Survey-backed contours | 14,208 | 20 ft | 35 ft | 60 ft |
| Approximated contours | 23,025 | 18 ft | 33 ft | 56 ft |
How to use maximum depth when planning a trip
Start with the number, then make it earn its place on the screen.
- Find the deepest contour or depth label. Confirm where the stated maximum appears, if the map resolves it.
- Trace the route back toward shore. Look for the points, breaks, channels, humps, or flats that connect deep water to feeding water.
- Scale your attention to the lake. In a 20-foot lake, a drop from 6 to 12 feet may be major. In a 150-foot lake, that same change may be one small shelf.
- Check the data label. Treat a precise turn in an approximated contour as a hypothesis. On a survey-backed map, check the source details and survey age before assuming precision.
- Adjust for current conditions. Reservoir drawdown, drought, flood operations, and seasonal water-level changes can shift the depth beneath your boat without moving the printed lines.
- Use sonar and your eyes as the final check. Fishing maps are planning tools, not navigation products.
The habit to avoid is turning “maximum depth: 60 feet” into “fish should be in 60 feet.” Maximum depth describes the basin. Fish position is a moving biological question.
Methodology
We captured the public DepthScout catalog on August 17, 2026. The manifest contained 37,672 unique waters: 37,234 classified as lakes, 387 as rivers, and 51 as saltwater segments. Rivers and saltwater segments were excluded before calculating the lake distribution.
Every lake record had a positive maximum-depth value. We applied one additional physical-plausibility screen: values above 6,000 feet were excluded from summary statistics. That ceiling sits above the published depth of Lake Baikal, which USGS identifies as the world's deepest freshwater lake. One record failed the screen. We left it in the downloadable dataset with included_in_analysis=false and an exclusion reason rather than silently deleting it.
The final analysis included 37,233 records. We sorted their maximum depths and calculated the 25th percentile, median, and 75th percentile with linear interpolation. Threshold percentages use exact row counts and are rounded to one decimal place for display.
Depth-data groups come from the same public labels used on DepthScout lake pages. A source key containing survey is classified as survey-backed; all other displayed contour sets are classified as approximated. This grouping describes contour provenance only.
Limitations
This report describes one product catalog at one moment. It is not a census of every lake, a probability sample, or a ranking of regions.
Catalog coverage is uneven. Some public agencies publish comprehensive lake inventories; others publish a small set of popular waters or no reusable depth records. The resulting geographic mix affects the overall distribution.
The maximum-depth field also comes from many source systems. Survey dates, measurement methods, vertical datums, units, rounding, and current water levels vary. We screened for missing, non-positive, and physically implausible values, but we did not independently resurvey 37,233 lakes or verify every number against its original record.
Maximum depth does not describe average depth, lake volume, bottom slope, habitat quality, public access, fishing quality, or safe navigation. The report does not infer any of those measures.
Data, sources, and citation
Download the row-level lake maximum-depth snapshot and read the data dictionary, calculation rules, and limitations.
Primary references:
- DepthScout data and methodology
- NOAA: What is bathymetry?
- USGS lake-data definitions for maximum and mean depth
- USGS: Lake Baikal, the world's deepest freshwater lake
- Wisconsin DNR: inland lake depth and stratification
- EPA dissolved-oxygen factsheet
Suggested citation:
DepthScout Research. “The 33-Foot Lake: What 37,233 Maximum-Depth Records Reveal.” August 17, 2026. https://www.depthscout.com/research/how-deep-are-fishing-lakes-2026
What we want to measure next
Maximum depth is the easiest lake-depth statistic to find and one of the easiest to misuse. A stronger future analysis would add lake area and volume, distinguish natural lakes from reservoirs, and compare maximum depth with the amount of bottom in each depth band.
That requires consistent geometry and source metadata across the catalog. Until then, 33 feet is a useful middle—not a shortcut for what any one lake looks like below the surface.