Tortuguero's beach is one of the great turtle nesting sites of the Caribbean. Green turtles are the main draw, especially from July to October, while other turtle species nest in smaller numbers at different times of year.
Night turtle walks are tightly controlled for good reason. You must go with an authorised guide, keep lights and cameras away, and follow instructions quietly. Done properly, watching a turtle haul itself out of the surf and dig a nest is unforgettable; done carelessly, it can disturb the animal.