NBM Dive Site Resource
John McGean
Michigan Thumb, Michigan, United States
TECHNICAL DIVE ONLY — John McGean is a documented wreck in the Thumb Area Bottomland Preserve’s official inventory, listed at approximately 195 feet.
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Historic Photograph
Aquatic life at this dive site
What divers may encounter
Three reviewed connections are featured here. Sightings vary by season, conditions, and chance, so they are never guaranteed.
Lake Trout
Salvelinus namaycushThe John McGean rests at 195 feet in Lake Huron. NOAA identifies lake trout as a native predator occurring across inshore and offshore depths; any encounter at this technical depth remains condition-dependent.
Knepp Timothy, U.S. Fish and Wildlife ServiceOpen Aquatic Life Profile →
Lake Whitefish
Coregonus clupeaformisNOAA identifies lake whitefish as an important Lake Huron fish stock. Divers may see passing fish near deep structure, but sightings are never guaranteed.
Seb951Open Aquatic Life Profile →
Burbot
Lota lotaNOAA notes that burbot often appear at deeper Lake Huron shipwrecks. They are most plausible close to the bottom and shaded structure.
USFWS Mountain-PrairieOpen Aquatic Life Profile →
Site media
Photographs
Three views rotate from the published gallery on each visit.
Contributor media
Dive videos
Three featured video positions are reserved on every profile.Published reference location
Location map
The marker shows the public coordinates associated with this profile. Confirm current access, moorings, and departure details before the dive.Map data © OpenStreetMap contributors
Recent field observations
Diver-reported temperatures
Automatically checked observations from dives during the past 14 days. Three reports are visible at a time; scroll for more.A report that passes the automatic checks will appear here with the dive date, diver’s display name, and temperatures at each depth.
Reports are automatically checked for plausible dates, depths, and temperatures. They are observations, not forecasts; confirm conditions before diving.
Seasonal planning reference
Typical monthly conditions
Long-term averages, not a forecast. Actual air and water conditions can change quickly and may vary across the site.Moderate-confidence match — Matched by documented Great Lakes port/area. Air and surface-water values are regional planning averages. No bottom-water line is published because a comparable depth-specific record has not yet been verified.
| Month | Average air | Surface water | Bottom water | Bottom measurement depth |
|---|---|---|---|---|
| Jan | 25.8°F / -3.4°C | 34.1°F / 1.2°C | No reliable record | — |
| Feb | 28.0°F / -2.2°C | 33.8°F / 1.0°C | No reliable record | — |
| Mar | 37.2°F / 2.9°C | 35.9°F / 2.2°C | No reliable record | — |
| Apr | 48.9°F / 9.4°C | 37.0°F / 2.8°C | No reliable record | — |
| May | 60.3°F / 15.7°C | 40.0°F / 4.4°C | No reliable record | — |
| Jun | 69.9°F / 21.1°C | 51.1°F / 10.6°C | No reliable record | — |
| Jul | 74.1°F / 23.4°C | 63.9°F / 17.7°C | No reliable record | — |
| Aug | 72.3°F / 22.4°C | 68.6°F / 20.3°C | No reliable record | — |
| Sep | 64.9°F / 18.3°C | 64.8°F / 18.2°C | No reliable record | — |
| Oct | 53.0°F / 11.7°C | 56.4°F / 13.6°C | No reliable record | — |
| Nov | 41.2°F / 5.1°C | 48.2°F / 9.0°C | No reliable record | — |
| Dec | 31.3°F / -0.4°C | 44.0°F / 6.7°C | No reliable record | — |
NOAA NCEI 1991–2020 U.S. Climate Normals — Detroit Metro, MI
1991–2020 climate normalsReview source ↗NOAA NCEI Coastal Water Temperature Guide — South Huron
Historical monthly station averagesReview source ↗Bottom temperature is never inferred from surface temperature. A blank month means no reliable depth-specific average is available. Data reviewed 2026-08-26.
Why divers know this place
Highlights
Officially documented Thumb Area Bottomland Preserve site.
Regional context
Located within
Before you arrive
Access notes
Primarily boat access; confirm coordinates, mooring status, weather and preserve guidance before departure. Published coordinates support regional discovery and are not a substitute for current navigation, active mooring information, operator guidance, permits, weather, or a dive plan.
Plan within your training
Conditions and hazards
Cold water, open-water conditions, changing visibility, entanglement and overhead/penetration hazards around wreckage. Depth may create decompression obligations; cold water, limited visibility, entanglement and overhead wreckage require site-specific technical planning.
Independent resource notice
This record is a starting point for independent verification. Access, closures, moorings, weather, currents, depth, visibility, operator availability, and site conditions can change without notice. Confirm current information with the responsible operator, property owner, managing authority, or another qualified local source before planning or attempting a dive.