Trails that float on the surface of the water are quite rare. They are covered briefly here. The Missoula Technology and Development Center is planning a more detailed report on this topic.
Most floating trails are engineered structures, like docks, that float on watertight drums, polystyrene-filled corrugated plastic pipe, or other specialized floating systems. Rely on your engineering and landscape architectural staff to help you design a functional, attractive system.
A floating trail needs solid anchors at each end. Depending on the length of the floating trail and the expected water condition, the anchors may be timber deadmen (buried anchors), helical piles, concrete deadmen, or long wooden piles. Two cables, connected to these anchors and the opposite ends of each float, hold the floats in place. The trail must be straight between anchor points. Bends in the route require intermediate anchor points for the cables. If there is any current, an additional cable brace should be attached to the floats toward the middle of the span to hold them in place against the current. This cable brace must also be anchored on both ends. You may need to install cable braces on both sides of the floating trail to hold it in place (figure 67).
A floating trail tends to bob around, creating an unsteady tread surface. Such trails may not be suitable for all users. During periods of rough water, the floating trail may have to be closed.