Drive to Caño Negro Wildlife Reserve near the Nicaraguan border. This protected area embraces a lowland forested wetland and was established to be a safe haven for migratory birds. You'll be driven to the small town of Los Chiles to begin your nature cruise. It's an enchanting three hour boat trip up the Río Frío through the reserve to Caño Negro lake, a shallow overflow from the river in the wet season (it's dry in March-April). En route you'll be looking out for sloths, monkeys, caimans, bats and tropical flora. Finally, settle down to a lunch at a restaurant on the river bank, after which you continue to the border crossing point into Nicaragua.
The rest of today’s adventurous journey is by motor launch on the stately and serene Rio San Juan, which connects Lake Nicaragua with the Caribbean coast. The trip is delightful, the banks sheltering a mix of farmland (cattle, fruit, maize) and pure tropical forest, speckled with egrets and other, more timid riverine creatures. It’s increasingly wild, tightly forested and unpopulated, so it comes as a shock to round a bend in the river and be confronted by a huge stone fortress atop a hill overlooking the little river port El Castillo. The fort was built by the Spanish to protect the affluent city of Granada from attacks by pirates. Your hotel is on the narrow ‘main street’ of the vehicle-free town.
After nightfall, go searching for caiman under the moonlight, accompanied by a specialist guide. As you glide through the darkness, a journey orchestrated by the nocturnal sounds of the rainforest, the guide’s spotlight will reflect the beady red eye of watchful caiman as they rest in the vegetation along the water's edge. You may be able to get up close to one to see its delicate markings and maybe its razor-sharp teeth. The baby caiman are particularly endearing, and could fit into the palm of your hand (don’t pick one up though!).