This is a close up of a caiman. Caiman are similar to crocodiles, only smaller. They are only about 2.5 meters (8 ft.) in length. They are not as aggressive as crocodiles and are generally considered not to be a threat to people. You will also notice that they do not have as large a set of teeth as crocodiles, and they do not have the the large tooth that protrudes upward from the lower jaw about 4 teeth back from the tip of its mouth.
Caiman are common in Tortuguero. On our boat ride meandering through the backwaters of Tortuguero, we saw more than 10 caiman in three different locations within the span of about an hour.
We saw some children swimming in the main river at the town of Tortuguero. Although that was not in the narrrow waters within the park where we saw the caiman, that would still be too close for my comfort.