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Great Lakes lake depth maps

How deep is Lake Ontario?

Lake Ontario is 802 feet deep at its deepest point and averages 283 feet, according to the US EPA and NOAA GLERL physical features tables (measured at Low Water Datum). Separately, the NOAA contour set behind our interactive map below reaches 690 feet at its deepest line, across 11 depth bands and 529 contour lines.

Published figures: US EPA, Physical Features of the Great Lakes

Data: NOAA National Centers for Environmental Information, Great Lakes bathymetry (public domain). Source data checked and prepared by Jordan Carter, founder of GilledIt · page updated

Lake Ontario depth map and depth facts

Data: NOAA National Centers for Environmental Information, Great Lakes bathymetry (public domain), retrieved August 2026 · depths change over time · not for navigation

Lake Ontario depth facts
Maximum depth (published)802 ft (EPA / NOAA GLERL, Low Water Datum)
Average depth (published)283 ft
Deepest contour on this map690 ft (11 depth bands)
Contour sourceNOAA NCEI Great Lakes bathymetry (public domain)

Reading the Lake Ontario depth map

The contours here map whole-lake basin structure from NOAA's open-lake survey lines, which run 500 to 2,500 meters apart. That scale shows you where the shelf breaks toward deep water, how steeply the bottom falls away from your stretch of shoreline, and where the major basins sit. It will not resolve an individual reef or drop-off, so treat it as trip-planning context alongside a proper nearshore chart, not as a spot-finding tool. And a safety note that matters on water this size: conditions and ice on the open Great Lakes are not comparable to an inland lake, so never apply inland ice or small-water judgment out here.

Lake Ontario depth map FAQs

How deep is Lake Ontario?
Lake Ontario is 802 feet deep at its maximum and averages 283 feet, per the US EPA and NOAA GLERL physical features tables (Low Water Datum). The NOAA contour set behind our map reaches 690 feet at its deepest line.
Where is the deepest part of Lake Ontario?
The deepest water in Lake Ontario lies in the Rochester Basin, off the southeastern shore. Note the distinction our pages keep: the deepest contour in the NOAA dataset behind our map is the 690 ft line, while the lake's published maximum of 802 ft lies deeper than the mapped contours reach.
How accurate is this Lake Ontario depth map?
The contours come from the NOAA NCEI Great Lakes bathymetry survey, retrieved August 2026 and last rebuilt on August 19, 2026. Depths change over time with water levels and sediment, so treat this map as a planning guide for fishing, and never use it for navigation. The NOAA compilation maps open-lake survey lines spaced 500 to 2,500 meters apart, so it shows whole-lake basin structure rather than individual reefs or drop-offs.

Compare all five: Great Lakes depths compared · US fishing license guide

Depth maps for lakes near Lake Ontario