The Marina Loop, like the entire Switchgrass Trail, is phenomenal. The Switchgrass Trail system may completely change your view of cross-country drives across Kansas from here on out. The trail crews who built this squeezed every last drop out of the landscape to create a rolling hilly singletrack that at times is only a couple feet from a 10-20' drop off into Lake Wilson. After entering Wilson State Park and crossing the bridge across the reservoir, there is a parking area on your right. This is a great access point for the Marina Loop and the Hell Creek Loop
The Switchgrass Trail was built as a mountain bike trail and to limit erosion and maintain the singletrack, the trail is typically ridden clockwise. As a hiker, please stay on the singletrack (sometimes it's as narrow as 6" wide!) and you may find it better to hike counter-clockwise so you can see mountain bikers coming along.
Start by descending out of the parking lot to the northeast towards the bridge. Within 100' of going under the bridge you'll take a left onto a very short connector trail and take another left so that you now have the lake on your right. (Taking a right at either of these intersections leads you to the Hell Creek Loop
). The trail hugs the edge of the lake and has a surprising level of exposure as you are hiking atop sandstone outcrops that are reminiscent of Southern Utah. It's hard to believe that you're still in Kansas.
The trail continues to contour the lake and switchbacks back and forth across the terrain to utilize all the land, at times you'll be hiking and see a parallel trail 30' away which you'll soon be on. This labyrinthine trail has many short connectors to make loops of varying sizes possible, and you are usually still within sight of the parking lot despite having gone several miles. When you reach the road, continue straight to enter the Golden Belt Loop
or take a left on the road and re-enter the Marina Loop 100 yards later on the left. From here, the trail takes a relatively direct path back to the parking lot.
Though typical trail etiquette expects bikers to yield to hikers/runners, it may be a courteous act to yield to mountain bikers on this trail as it is so clearly a mountain bike trail for mountain bikers. That being said, it's still a phenomenal trail to hike (and break up the drive across Kansas!)