At Itaipu lake (the artificial lake of Itiapu dam) you can practise all kind of water sports: fishing, windsurf, kayaking, sailing...
En el lago de Itaipú (el lago artificial de la represa de Itaipú) se pueden practicar todo tipo de deportes acuáticos: pesca, windsurf, canotaje, vela...
Visiting the national park, you'll have many different sporting choices. Obviously, you can spend all day hiking around the trails and seeing spectacular views of the falls, but for a slightly different perspective, you can also ride a boat at high speeds directly toward the falls or take a more leisurely pace along the Rio Iguacu. Contact the Macuco Company (045 574 4244) for information. If you want something a little more exhilarating, you can even go repelling off one of the cliffs along the Rio Iguacu near the falls. Contact the tourist information office in town for info on that one.
This is a view from my hotel room balcony down to the pool. It gets pretty hot in Iguacu and there's no better way to cool off than to take a quick dip in the pool. Most hotels in the area are modern and will have a clean and safe pool to enjoy.
There is Rafting in Rio Iguacu, right under the Waterfalls. The only Rafting company is the Macuco Safari, the same company that serves the Waterfalls boat ride.
The rafting is too light, so if you are professional you will hate it. The best part is when the Instructor invites you to a swim at the river, and you can jump from the boat and enjoy the Iguacu River.
If you pay for the Rafting, you can also take the regular Boat Ride, that takes you close to the waterfalls (beneath one of them, actually).
If you pay only for the regular Boat Ride, you won't be able to jump to the river, but still can go pretty close to the waterfalls.
Equipment: If you plan on going either the regular Boat Ride or the Boat Ride plus Rafting, you should take a towel and swim clothes, because in both rides you will get VERY WET (like in a swimming pool). Also take some deodorant, because the lifesaving equipment really stinks (they told me they wash it everyday, but I doubt it). You can take a backpack and leave it with your belongings in the platform, but take some plastic covers to put your wallet and camera inside, if you want to take them with you in the ride. I don't belive anyone there would rob your things, but precaution is never too much right?