This is a swampy area approximately 3 miles long and well over a mile wide. Access to the water is limited to non-powered craft and there is a short (300') carry to put in from the small parking area.
We went later on in a hot, dry summer so there was a considerable amount of floating duckweed, lily pads, etc. The water generally isn't very deep (2-6'), so novices or poor swimmers can usually just stand up if they dump.
There are many kinds of wildlife incl. Canada geese, herons, woodpeckers, turtles, fish...
Consider going earlier in the season to avoid weed mats and low water obstacles.
Pretty much nothing there at the site. You can stay at places in the surrounding towns of Dansville, Mt. Morris and Geneseo. Letchworth State Park isn't far away. That's a good trip on its own......
Find Conesus Lake in a map of New York. It'll be the westernmost Finger Lake, just east of Rte 390. If coming from the south, get off Rte 390 at Dansville. Take Rte. 256 north out of Dansville. You'll see wildlife refuge signs on the right as you get close. There'll be a small road on the right just before the south end of the lake, take another quick right into the parking lot.
From the north, get off Rte 390 at Lakeville and take 256 south along the lake to its south end. The little road will be on the left.
Just a standard map to get you there. You may want to bring a compass to navigate back through the cattails and small islands.