Seminole State Forest Trail is a 12.7 mile loop trail located near Eustis, FL that features a lake. The trail is good for all skill levels offers a number of activity options.
We hiked the Florida Trail segment that runs through Seminole SF as a there-and-back day hike (around 15.2 miles, from Cassia to Bear Pond and back). Despite its length, this was a very pleasant and relaxing hike through a nice mix of habitat types--primarily pine flatwoods, with one long stretch through palmetto scrub and brief traipses through hardwood hammocks and past lakes, marshes and creeks. There's a good map at OutInTheBoonies.com (http://www.outintheboonies.com/Seminole_Forest/topo_map.jpg) and a good trail description at FloridaHikes.com (http://floridahikes.com/florida-trail-seminole-state-forest). The trail is mostly well-blazed and easy to follow, with a couple turns in the northern half that are easy to overshoot as the path briefly merges onto old forest roads then veers off again--not a big deal, just backtrack a bit if you haven't seen a blaze recently. The section through palmetto scrub is completely exposed, so be sure to take plenty of water if it's a hot sunny day, or a raincoat if it's drizzly (on the bright side, you'll almost certainly see several scrub jays out there). Blackwater Creek, about midway between the two trailheads, makes a lovely picnic spot; the Boy Scout shelter (near the Bear Pond end), would be a decent stop too--nothing much to look at, but it does offer protection from the elements and a comfortable place to sit.
I led a small group hike beginning at the Cassia trail head last Saturday (8/21). The trails were in good shape and other than crossing the path of a few horseback riders we had the trail to ourselves. August really is NOT the time for serious hiking in Florida: I sweated through two tees on the trail. We did approx. 6.3 miles. No wildlife due to our later start and the opressive humidity. I would recommend this trail without amy reservations. The habitat is typical Florida scrub pine and oak eith a sampling of grass prairie. If you go be sure to pick up the literature on the Florida Trailwalkers program managed by the state's Division of Forestry.