Smaller ocean ships of 3,000 tons and 7.9 m ( 26 ft ) draft can reach as far as Iquitos in Peru , 3,700 km ( 2,300 miles ) from the sea . Smaller ocean vessels of 3,000 tons or 9,000 tons and 5.5 m draft can reach as far as Iquitos , Peru , 3600 k from the sea .