Use sunset as your turnaround alarm.
Mt. Gog and Mt. Magog rise directly over the water on either side, which is unusual for a lake you can reach in an afternoon. The catch is the profile: you climb a ridge from Tony Grove, then drop steeply to the shore, which means the tired part of your day is a climb, not a coast. There are campsites and a toilet on the north side if you want to stay. Brook trout patrol the shallows and are easy to spot from the bank.
Turquoise lake between two limestone peaks; brook trout cruising the shallows.
2 liters water, trail shoes, sun layer, snacks, small first-aid kit.
Make it a weekend: Tony Grove Campground (Camping, 2 mi) · Sunrise Campground (Bear Lake) (Camping, 9 mi) · Guinavah-Malibu Campground (Camping, 11 mi) · Logan River 1st-3rd Dams (Fishing, 15 mi)
More hikes nearby: Naomi Peak (Hike, 2 mi) · Wind Caves (Hike, 12 mi) · Ben Lomond via North Skyline (Hike, 42 mi) · Waterfall Canyon (Hike, 52 mi)