Explore inland water with context

Find clearer water.
Know what’s below.

OWMaps brings historical water clarity, lake depth maps, and lake context into one accessible place for open-water swimmers, freedivers, and scuba divers.

Explore 136,977 lakes and reservoirs across the contiguous United States using historical estimates from 1984–2020.

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See where the data comes from ↓
“This has the potential to be the best thing to happen to the OWS community.”
Ben · Triathlete from Minnesota
“The Zillow of open-water swimming.”
Anonymous

Built for the water-curious

A clearer way to discover inland water.

Open-water swimmer crossing a calm forest-lined lake

Open-water swimmers

Discover lakes by long-term clarity and physical characteristics.

Freediver descending through clear freshwater

Freedivers

Find promising water and understand whether depth information is surveyed or modeled.

Scuba diver exploring a clear freshwater lake

Scuba divers

Bring clarity history, depth context, and source provenance into early site research.

Research context, not a safety assessment.

OWMaps does not certify current visibility, access, suitability, navigation, or safety. Always check local conditions, weather, water quality, boat traffic, temperature, regulations, and site access before entering the water.

Transparent by design

Know what you’re looking at.

Every layer comes from a named source. Verified survey contours and modeled depth estimates are kept visually and verbally distinct throughout OWMaps.

Water clarity

LAGOS-US LANDSAT v1.0

Quality-controlled Landsat estimates of Secchi depth, chlorophyll-a, and turbidity from 1984–2020.

Satellite estimatesLake identity

LAGOS-US LOCUS v1.0

Lake names, locations, surface area, elevation, shoreline geometry, and freshwater connectivity.

Lake catalogVerified depth

Minnesota DNR Lake Bathymetry

Published government depth contours for conservatively matched Minnesota lakes.

Measured contoursVerified depth

MassWildlife Inland Water Bathymetry

Published MassGIS depth contours for conservatively matched Massachusetts lakes and ponds.

Measured contoursMinnesota lake profiles

Minnesota DNR LakeFinder

Official morphology, resource availability, and invasive-species context loaded by DNR lake identifier for conservatively linked Minnesota lakes.

Official lake factsModeled depth

GLOBathy

Statistical maximum-depth estimates used only as a clearly labeled fallback—not measured bathymetry.

Modeled estimateModeled shorelines

HydroLAKES

Shoreline geometry used to approximate GLOBathy depth contours. Licensed under CC BY 4.0.

CC BY 4.0Topographic basemap

Esri World Topographic Map

Topographic cartography and geographic context from Esri and its contributors.

Esri basemapSatellite basemap

Esri World Imagery

Global satellite and aerial imagery shown as optional geographic context; imagery dates and resolution vary by location.

Esri imageryMapped water access

OpenStreetMap

Community-mapped boat launches, kayak/canoe put-ins, beaches, swimming areas, and water access points. Missing features do not prove access is absent.

Community mapped