Wikipedia
A railroad car float or rail barge is an unpowered barge with rail tracks mounted on its deck. It is used to move railroad cars across water obstacles, or to locations they could not otherwise go, and is towed by a tugboat or pushed by a towboat. As such, the car float is a specialised form of the lighter, as opposed to a train ferry, which is self-powered.
Usage examples of "car float".
After that Coyote and Art stood there, and watched the car float over to the cable and rise through the valve door and disappear.
The process was infuriatingly slow, in the fractional gee used to make the car float, but this was all we had.
He saw the left front wheel of the green car float past his own, then the right wheel of his car crawled over the guard rail, his car slid after it and hung poised on the edge of the palisade.
Sir George managed to say in a nearly normal voice, and watched the silent air car float away across a sky heavy with Shaakun's equivalent of ravens.
Sir George managed to say in a nearly normal voice, and watched the silent air car float away across a sky heavy with Shaakun’.