The excellent GoWaterfalling website has an entry for Spray Falls that says in part:
Spray Falls is the remotest, and perhaps the most impressive of the several waterfalls in Pictured Rocks National Lakeshore. The 70′ waterfall plunges over the cliffs at Pictured Rocks and lands directly in Lake Superior.
The falls is right on the edge of the cliffs, and the creek has not cut back into the cliffs at all, so it is impossible to view the falls from the front unless you are on the water. The cliffs are sheer for miles in both directions, so there is no way to get near the base of the falls without a watercraft. Lake Superior is too cold for swimming. :)
The Lakeshore Trail passes right over the top of the falls, and you can get right to the brink of the falls. Be careful because the cliffs are undercut and unsafe in many places. About 1/4 mile east of the falls there is a safe lookout point from which you can get a nice, but distant, side view of the falls. There is a sign marking the lookout.