The lake bed in 3-D: deep basin, drop-offs and shoreline. Shape estimated, not for navigation. Spot 1 (point drop-off) is open for everyone; the other 3 come with LakeScope PRO. Full screen
Grand Lake St. Marys
Mercer County, Ohio · 12,900 acres (20.1 sq mi)
51°F water, level 871 ft, calm this morning.
About Grand Lake St. Marys
In Mercer County, Ohio, Grand Lake St. Marys covers 12,900 acres; it is a reservoir. Grand Lake St. Marys was built in the 1840s as a feeder reservoir for the Ohio and Erie/Miami and Erie Canal system and was, at the time, the largest artificial lake in the world.
From end to end it runs about 8.3 miles and its shoreline adds up to about 27 miles. At about 870 ft above sea level, it follows the seasons of the region. Celina is right by the lake.
- Size
- 12,900 acres (20.1 sq mi)
- Shoreline
- About 27 miles
- End to end
- About 8.3 miles
- Elevation
- About 870 ft
- Type
- Reservoir
- County
- Mercer County
The lake from above
Best fishing times
Friday Good
- 6:45 am – 9:00 amsunrise
- 3:45 pm – 5:15 pm bestsunset, moon overhead · wind 10 mph
Saturday Good
- 6:45 am – 9:00 amsunrise · wind 7 mph
- 3:45 pm – 6:00 pm bestsunset, moon overhead · wind 13 mph
Based on sun and moon times and the wind forecast. A guide, not a promise. The app shows the whole week.
Fish in Grand Lake St. Marys
Grand Lake St. Marys holds crappie, largemouth bass, yellow perch, bluegill and sunfish, walleye and catfish. With the surface at 51°F, the notes below say which of them should be biting.
- FairCrappie
Schooled on deeper brush piles. Fish small jigs slowly.
- FairLargemouth bass
Cooling down. Try slow baits on points and deeper channel edges.
- GoodYellow perch
Schooled near weed edges and soft bottom.
- SlowBluegill and sunfish
Cold. Deep and hard to tempt. Use tiny baits.
- GoodWalleye
Good cool-water bite, best at dusk and after dark.
From today's water temperature and the season. A guide, not a promise.
Fishing spots
- 1Point drop-off
The bottom falls away fast off this point; fish rest deep and move up the slope to feed.
- 2
- 3
- 4
3 more spots with LakeScope PRO: fish, depth band, water temperature, best time and bait for each.
Picked from the shape of the lake bed. A guide, not a promise.
Water temperature
At the surface, seen .
Water level
7-day trend: not enough daily readings yet.
Latest reading .
Ice
Open water
Ice thickness is an estimate from air temperature, not a measurement. Check the ice yourself before going on it.
Weather and wind
Sunrise 7:22 am · sunset 5:21 pm · waxing crescent moon (lake time).
Towns and places to stay near Grand Lake St. Marys
- Celinaon the shore
- Saint Marysabout 1.5 mi east
- Coldwaterabout 3.5 mi southwest
- New Bremenabout 6 mi southeast
Prices and availability come from booking partners; we may earn a commission at no cost to you.
Questions about Grand Lake St. Marys
What fish are in Grand Lake St. Marys?
Grand Lake St. Marys holds crappie, largemouth bass, yellow perch, bluegill and sunfish, walleye and catfish. Check the state fish and wildlife agency for stocking and limits.
How deep is Grand Lake St. Marys?
We have no published depth for this lake. The 3-D view gives an estimated shape of the bed: where the deep basin and the drop-offs are. Not for navigation.
How big is Grand Lake St. Marys?
12,900 acres, with about 27 miles of shoreline.
What town is near Grand Lake St. Marys?
Celina is on the shore; Saint Marys is about 1.5 miles east.
What is the water temperature at Grand Lake St. Marys today?
The surface was about 51°F on the latest clear reading. The page updates every day.
Grand Lake St. Marys on your phone
The whole week of bite times, lake alerts and the 3-D view, every morning.
