Heading to or from Barra via the Sarapiquí area in the Zona Norte entails a trip along the Río Sarapiquí to the mighty Río San Juan. Flowing from Lago de Nicaragua to the Caribbean, the San Juan marks most of Costa Rica’s border with Nicaragua, and the entire northern edge of the Refugio Nacional de Vida Silvestre Barra del Colorado. It’s theoretically in Nicaraguan territory, but Costa Ricans have the right to travel on the river – though this eastern stretch of the San Juan has been the source of a diplomatic dispute between the two countries since late 2010 (see Invasion by internet). There isn’t, however, an official entry point between the two countries so it’s technically illegal to cross into either country along this stretch. For more details on crossing into Nicaragua.
One bizarre phenomenon local to this area is the migration of bull sharks from the saltwater Caribbean up the Río San Juan to the freshwater Lago de Nicaragua. They are unique in the world in making the transition, apparently without trauma, from being saltwater to freshwater sharks.
You’ll notice much evidence of logging in the area, especially at the point where the Sarapiquí flows into the Río San Juan – the lumber industry has long had carte blanche in this area, due to the non-enforcement of existing anti-logging laws. The Nicaraguan side of the Río San Juan, part of the country’s huge Reserva Indio Maíz, looks altogether wilder than its southern neighbour, with thick primary rainforest creeping right to the edge of the bank. Partly because of logging, and the residual destruction of its banks, the Río San Juan is silting up, and even shallow-bottomed lanchas get stuck in this once consistently deep river. It’s a far cry from the sixteenth and seventeenth centuries, when pirate ships used to sail all the way along the Río San Juan to Lago de Nicaragua, from where they could wreak havoc on the Spanish Crown’s ports and shipping.