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Lakes → Ohio → Grand Lake St. Marys

Grand Lake St. Marys

Ohio · Reservoir impounded 1845 · near Celina

13,500 acres 7 ft deep 2 ft clarity Water D
Compare
5.6SCORE
Survey summary · Ohio
13,500
Surface acres
7 ft
Max depth
52 mi
Shoreline
2 ft
Typical clarity
871 ft
Elevation

Grand Lake St. Marys covers 13,500 acres in Ohio and drops to 7 feet at its deepest point. It is a reservoir impounded in 1845 and managed by Ohio DNR. Level is unusually stable, which protects dock usability and shoreline appearance year round. Clarity is limited, which is typical of productive fisheries but worth seeing in person if you are swimming daily. Short-term rental posture: Mercer/Auglaize County. Confirm at the municipal level before underwriting rental income.

What stands out

  • Very stable water level year-round
  • Fishing
  • Boating

Watch outs

  • Nutrient-rich water; seasonal algae blooms are possible

Score breakdown

WATER RECREATION VALUE ACCESS INVESTMENT
Water 2.7
Recreation 5.5
Value 6.2
Access 6.1
Investment 8.4

Each axis is computed by published formula from this lake's own attributes. How we score.

Water quality grade
Water A
ExcellentClear, low-nutrient water. Typically oligotrophic with high clarity and little seasonal algae.
Water B
GoodHealthy water with moderate clarity. Some seasonal variation, no persistent problems.
Water C
FairProductive water — good fishing, reduced clarity. Algae possible in late summer.
Water D
PoorNutrient-rich or heavily drawn down. Swimmable conditions vary; check before you rely on them.

Computed from measured clarity, trophic state, and drawdown magnitude — not an opinion. See the formula.

Overall score, 1–10
8.0+
ExceptionalStrong on every axis we measure.
7.0–7.9
StrongClearly above average, usually with one standout axis.
6.0–6.9
SolidA good lake with a trade-off worth understanding.
5.0–5.9
MixedReal strengths and real compromises.
Under 5
CompromisedSomething material — volatility, water quality, or access.

Weighted: water 26% · recreation 22% · investment 20% · value 18% · access 14%.

Fishery

CrappieBluegillCatfishLargemouth bass

On the water

FishingBoatingCamping
Live from USGS gauge 04183500. These are direct sensor readings, not estimates.
26.10 deg C
Temperature
2026-08-04
6.46 ft
Gage height
2026-08-04
9.40 FNU
Turbidity
2026-08-04

Gauge history

Daily values from USGS. Loading up to one year.

Where it is

Location

No NHD boundary matched this water body, so the marker shows the mapped centre point.

Depth profile

SURFACE 7 ft max avg 2 ft

Idealized cross-section. Max depth 7 ft, average 2 ft. Depth at a specific dock depends on local bathymetry — verify at the property.

Level behaviour

Level stabilityStable Typical drawdown2 ft Drawdown seasonWinter Trophic stateHypereutrophic Typical clarity2 ft Water quality gradeD Elevation871 ft Managing authorityOhio DNR

Dock & shoreline

Permitting authorityOhio DNR Wake / speed rulesOpen water
A dock is never guaranteed. Confirm in writing with Ohio DNR that the specific parcel is eligible before you remove contingencies.

Short-term rental posture

Mercer/Auglaize County

Generally permitted, but rules change. Confirm the specific municipality and any HOA covenant.
Model rental income →
Modeled estimates. Market figures are derived from lake attributes and regional patterns, not from MLS data. Treat them as a starting point, not a comp.
$235,000
Median waterfront
$2,482
Per shoreline foot
+6.3%
Year over year
30
Est. inventory
60
Avg days on market
$485
Est. nightly rate

Rental snapshot

Modeled occupancy66% Booked nights / yr173 Gross revenue$94,150 Net operating income$45,330 Yield on median price19.29%
Open the full model →

What a median-priced home on Grand Lake St. Marys actually costs to carry, with waterfront-specific line items most calculators omit.

$2,338
All-in per month
$55,890
Cash to close + setup
$9,325
Beyond P&I, tax, insurance
Where the annual cost goes
$28,051 PER YEAR
Principal & interest $14,858 (56%) Utilities $2,700 (10%) Maintenance reserve (1.1%) $2,585 (10%) Property taxes $2,468 (9%) Hazard insurance $1,400 (5%) Shoreline / seawall reserve $960 (4%) Dock maintenance $900 (3%) Winterization / seasonal close $750 (3%)

Annual carry

Principal & interest$14,858
Property taxes$2,468
Hazard insurance$1,400
Flood insurance$650
Utilities$2,700
Maintenance reserve (1.1%)$2,585
Septic service$520
Well & water testing$260
Dock maintenance$900
Winterization / seasonal close$750
Shoreline / seawall reserve$960
Total$28,051
Model your own numbers →

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