I’m grateful that it is only on the third day that Paul tells me that the Las Piedras River, where we have been boating, floating and swimming, my clothes perpetually wet from the afternoon plunges, is swimming with Piranhas. I knew about the Caiman, Spectacled and Yellow, that I’ve seen lounging on the banks, and scoot off whenever the boat comes near. I’ve tamed my response to snakes—an embarrassing nerve-jangling recoil—by understanding that every snake is more afraid of me than I am of it. But Piranhas, that’s news. I laugh and say: cool.