See Sea Turtles While Snorkelling Responsibly
A sea turtle can appear almost silently: a dark shape over sand, a slow turn of the shell and then a rise towards the surface for air. The encounter feels intimate precisely because the animal is following its own route rather than performing for the swimmer. Choose a place where snorkelling is lawful, conditions suit your ability and turtles are observed without being pursued. Enter for the reef and wider marine life, not a guaranteed close encounter. If a turtle appears, slow down, keep the required distance and allow it an unobstructed path. Follow the rules for that location. NOAA's general guidance says not to swim with, touch, chase, feed or attempt to interact with wild sea turtles; in Hawaii the recommended viewing distance is at least three metres. Use a responsible guide where needed, never stand on coral, know currents and exits, and wear a flotation aid if your ability or conditions require it. Count this complete after a lawful snorkel in which you saw a turtle from a respectful distance, or chose not to approach one. Add it if you want wildlife to feel close without making closeness the price the animal pays.