So we finally made it to the falls after 5 days of laziness in Puerto Iguazu. But we did it for real: Some Australian guys gave us secret directions to the dopest locals-only spot where you can swim under the falls. If anyone is going there, here it is-- Head down to where the boats go across to Isla San Marten. Take the boat across and head up the stairs that lead up in the forest on the island. Turn left and keep going a little ways. You will reach an observation point with a railing and a 'Do not Enter sign'. Ignore this sign. Straight ahead for will see a big opening in the rock wall. Climb across the rocks toward this opening. Cuidado, Miho! At the top you'll see a wrecked metal boat. Pass through the opening in the rock and turn right. You can swim in all the pools, and it's safe to cross from one to the next. The rocks block the edge so you can't get swept up. Go to the 3rd pool and you can get under one of the big falls. Enjoy!