Do objects float more easily in salt water or fresh water?

Objects float more easily in salt water, and the saltier the better.

Any solid object placed on the surface of a liquid displaces its weight in that liquid (up to a maximum of the object's own volume). Saltwater, or any solution containing solutes, is more dense than plain water, so less of it is displaced, and objects will not sink as far into it, i.e. they are more likely to float rather than sink.