Getting there & away
The road from Mercedes to Colonia Pellegrini (120km) is unsealed, and departures are limited. Bus services are unreliable and painfully slow, but theoretically leave Mercedes twice a day for Colonia Pellegrini (AR$20, four to five hours); check at the bus terminal information office.
A faster and more reliable way to get there is by combi or 4WD transport. At the time of research, these options were available departing Mercedes at 8am on Wednesday, Friday and Sunday (one-way/return AR$70/130) for the three-hour trip, returning from Colonia Pellegrini at 4:30pm on Tuesday, Thursday and Saturday. Check the schedule with the bus terminal or Delicias del Iberá hostel in Mercedes, or with Cristian (03773-15-730735), also contactable at Yacarú Porá restaurant in Colonia Pellegrini. At other times combis may leave according to demand. You can also charter your own transport; this costs AR$240 for as many people as you can fit in the vehicle. Arrange this through the hostel in Mercedes, or contact Beto (03773-15-515862), who lives opposite Hostería Ñandé Retá in Colonia Pellegrini. There may already be a trip arranged that you can join.
The road from Posadas is worse, but the same transport service leaves for Colonia Pellegrini at 8am on Wednesday, Friday, and Sunday (one-way/return AR$90/165; four to five hours), returning to Posadas at 4:30pm Tuesday, Thursday and Saturday. Drivers charge AR$480 for a charter to Posadas.