NBM Dive Site Resource
Mahoning
Port Washington, Wisconsin, United States
Wooden brigantine wreck near Port Washington within the Wisconsin Shipwreck Coast National Marine Sanctuary.
Save this dive site to your free member profile.
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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.
Smallmouth Bass
Micropterus dolomieuNOAA reports smallmouth bass as a dominant fish using warmer nearshore Great Lakes wreck and reef habitat in summer. Mahoning lies in about 60 feet of water, but sightings remain season- and condition-dependent.
Eric Engbretson, U.S. Fish and Wildlife ServiceOpen Aquatic Life Profile →
Rock Bass
Ambloplites rupestrisNOAA reports rock bass as a dominant fish using warmer nearshore Great Lakes wreck and reef habitat in summer. Divers may find them close to the scattered wooden hull and artifacts.
Sam Stukel/USFWSOpen Aquatic Life Profile →
Round Goby
Neogobius melanostomusNOAA identifies round goby among Lake Michigan bottom-habitat fishes and as common around Great Lakes hard structure. Look along the broken wreckage and sandy bottom.
Peter van der SluijsOpen 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.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 | 24.0°F / -4.4°C | 35.2°F / 1.8°C | No reliable record | — |
| Feb | 27.1°F / -2.7°C | 36.6°F / 2.6°C | No reliable record | — |
| Mar | 36.4°F / 2.4°C | 37.8°F / 3.2°C | No reliable record | — |
| Apr | 46.3°F / 7.9°C | 38.3°F / 3.5°C | No reliable record | — |
| May | 57.1°F / 13.9°C | 42.5°F / 5.8°C | No reliable record | — |
| Jun | 67.6°F / 19.8°C | 53.7°F / 12.1°C | No reliable record | — |
| Jul | 73.3°F / 22.9°C | 68.2°F / 20.1°C | No reliable record | — |
| Aug | 72.3°F / 22.4°C | 72.2°F / 22.3°C | No reliable record | — |
| Sep | 65.0°F / 18.3°C | 68.4°F / 20.2°C | No reliable record | — |
| Oct | 53.0°F / 11.7°C | 58.5°F / 14.7°C | No reliable record | — |
| Nov | 40.4°F / 4.7°C | 49.0°F / 9.4°C | No reliable record | — |
| Dec | 29.5°F / -1.4°C | 43.7°F / 6.5°C | No reliable record | — |
Wisconsin State Climatology Office — Milwaukee Climate Data
1991–2020 climate normalsReview source ↗NOAA NCEI Coastal Water Temperature Guide — Station 45007
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
Brigantine remains and protected maritime heritage setting.
Shipwreck-only module
The wreck
This section appears only on shipwreck records and brings the vessel, its loss, present condition, access, and responsible wreck-diving considerations into one place.
- Vessel type
- Brigantine
- Year built
- 1848
- Year sunk
- 1864
- Vessel length
- 119 ft
- Cause of loss
- Foundered under tow for repairs, December 2, 1864
- Present condition
- Historic sailing-vessel remains at recreational depth.
- Penetration guidance
- Interior spaces are overhead environments. Entry requires appropriate wreck training, equipment and a planned exit; depth alone does not establish suitability.
History and significance
Built at Black River, Ohio, Mahoning had a working Great Lakes career before grounding near Sheboygan during a November 1864 gale. A subsequent tow toward repairs ended in foundering off Port Washington. Two lives were lost.
Plan the trip
Dive boats that visit this wreck
Aquatic Adventures identifies Len-Der for Port Washington trips to this wreck; confirm the current date.
Open boat profile →Port WashingtonMolly V — Wisconsin Lake Michigan Dive CharterShipwreck Explorers LLCShipwreck Explorers publishes this wreck on Molly V's Wisconsin destination page and directs divers to its live schedule or charter-booking page.
Open boat profile →Regional context
Located within
Before you arrive
Access notes
Boat-access sanctuary site; verify current mooring and charter availability.
Plan within your training
Conditions and hazards
Cold water, variable visibility, fragile timbers, entanglement and boat traffic.
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.