Went on a group trip to Iguazú falls in September 1997. The journey was by bus and took 24 hours in each direction including stops for meals. The bus had a sight-seeing stop at Minas de Wanda on the outward journey and at a ruined Jesuit mission on the return journey. My hotel was in Foz de Iguaçu over the border in Brazil for three nights.
The first full day the group was taken to the Argentina side of the falls and walked the paths and walkways on the edge of the falls. Mid-morning it started to rain; then those wanted to ride an inflatable boat up to the falls were taken down to the rivers edge below the falls. Those who came prepared wore full rainwear; others like me had a basic plastic poncho. The inflatables went as close to the falls as possible without actually going under them. The noise was tremendous.
The next full day it was still raining and the group was taken first to see the Itaipu dam and then over the bridge into into Ciudad del Este, Paraguay (no border formalities). After an hour there we returned to Brazil and visited a bird zoo. By now the rain had stopped and we went to view the falls from the Brazil side.