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On Black Oak Lake, west of downtown Land O' Lakes, a black-and-white disk lowered on a line stays visible past 30 feet down, and some readings have gone past 50. That is why people up here call it the clearest lake in the state, and why every lakefront listing says so.
It is also a quiet, mostly wild lake of 564 acres with one public beach and one boat launch, both on the south shore. If you come to Land O' Lakes in summer and swim only once, swim here.
How clear is Black Oak Lake?
Black Oak Lake's water clarity typically measures more than 30 feet, according to the Black Oak Lake Preservation Foundation, with some readings above 50 feet. Clarity is measured with a Secchi disk, a black-and-white plate lowered on a line until it can no longer be seen.
Two things keep it that clear. It is a seepage lake, fed by groundwater rather than inflowing streams that carry silt and nutrients, and its shoreline is lightly developed, with fewer than 16 property owners per mile of shore. On a calm morning you can watch fish over a sandy bottom from a kayak, and the water reads as a pale aqua near shore.
The foundation has worked since the 1970s to protect the shoreline and monitor the water, and it is the reason much of the north shore is still wooded and undeveloped.
The lake by the numbers
Black Oak Lake covers 564 acres in Vilas County, with more than 7 miles of shoreline. It reaches 85 feet at its deepest point and averages 34 feet, which makes it one of the deeper lakes around Land O' Lakes.
The east side holds the deep water and the open views, good for a slow cruise. The west side is shallower and better for gentle paddling. There is one public boat launch, and motors are allowed on the lake.
Swimming at the public beach
The public beach on the south shore is the best swim in town, with a buoyed swimming area, restrooms and changing rooms, and a sandy bottom you can see well past where you can stand.
Watch children closely, since clear water makes depth hard to judge and the bottom is always deeper than it looks. Search for the Black Oak Lake public beach or boat landing in your map app. Both sit together on the south side, off the town roads west of County B's downtown stretch.
Boating and paddling
Paddlers and boaters launch from the ramp next to the beach. A canoe, kayak or paddleboard is the best way to see the clarity, because you can drift and look straight down.
Respect the shoreline. Most of it is private property, and the undeveloped stretches on the north side are the reason the lake stays this clear. Keep wakes down near shore, and do not tie up at private docks.
Fishing Black Oak Lake
Black Oak Lake holds panfish, largemouth and smallmouth bass and northern pike. Clear water makes fish wary, so lighter line, early mornings and evenings tend to do better than midday. The downtown tackle shop sells the license and live bait.
Rusty crayfish, an invasive species, have been recorded in the lake. Clean, drain and dry your boat and gear before and after every launch, especially if you have been on another lake that day.
When to go
For swimming, July and August are the months, when the shallow water near the beach has warmed. For paddling and photos, go early on a still morning, before wind and boat wakes ruffle the surface. The clarity only shows when the water is flat.
Spring and fall bring fewer people and cool, quiet water for paddlers and anglers, and in late September and early October the hardwoods around the lake turn color. Midday on a hot summer Saturday is the busiest time at the beach and the launch.
Who lives on the lake
Black Oak Lake is a lake of cabins and year-round homes, with boathouses tucked under the trees and a few long stretches of shore with nothing on them at all. Loons nest here, so bring binoculars.
Conserve School, a semester school for high school juniors focused on environmental stewardship, has its campus on the shore. The lake also has a long resort history: there was a Black Oak Lake resort from 1908 into the 1970s, and in the 1920s crews cut ice blocks from the frozen lake by hand. The Land O' Lakes Historical Society has photos of both.
The preservation foundation still holds the occasional lakefront picnic and boat parade in summer. Check local listings if you would like to see the lake at its most social.
Winter on Black Oak Lake
In winter the lake freezes over and the beach goes quiet. A snowmobile and ATV trail runs just south of the lake, so in January you are more likely to hear sleds than see anyone on the shore. Ice anglers fish the lake too. Check ice conditions locally before going out, every time.
Where to eat and sleep nearby
There is no restaurant or resort on the lake itself, so plan meals and beds around it.
For dinner, the Bear Trap Inn is on County B about 1.5 miles west of downtown, on your way back from the lake, with Friday walleye fish fry and Saturday prime rib. For lunch out that way, Forest Lake Cafe serves breakfast and lunch Wednesday to Sunday with a view over Moon Lake.
How it compares with the town's other big lakes
Black Oak Lake is the clear, deep, quiet one. The Cisco Chain of Lakes, farther west, is 15 lakes linked by channels, with more boats, more resorts and better walleye and musky water.
East of downtown, Lac Vieux Desert is the opposite of Black Oak: big, shallow and weedy, with wild rice, musky and the source of the Wisconsin River at its outlet. Seeing all three in one trip shows you how different lakes a few miles apart can be.
For the rest of the town, from the bike trail to the museum in an old ski chalet, see things to do around Land O' Lakes beyond the lakes.
Frequently asked questions
Published September 21, 2026
