For my fishing seats, I used an allen-head bolt and wing-nut combination with T-nuts on the backside of the carpeted plywood. This way, I don't have to use a wrench to secure the seats to the floor when I get to the water. "Finger tight" on the wing-nuts is plenty tight enough to keep them steady. And not having to keep a wrench nearby means one less thing which I am most definitely eventually going to drop into the water.
https://dl.dropboxusercontent.com/u/36457490/20150616_155427.jpg
https://dl.dropboxusercontent.com/u/36457490/20150616_155349.jpg
https://dl.dropboxusercontent.com/u/36457490/20150616_155427.jpg
https://dl.dropboxusercontent.com/u/36457490/20150616_155349.jpg