8:27 a.m. — We’re the first ones at the cenote! J. is very thorough in her pre-dive briefing. Before we gear up, she leads me from the parking lot to the cenotes to show me the route I will take. She mentions the steps leading into the cenote are very slippery and to hang tight when I have all my heavy gear on. Since freshwater and saltwater have different densities, she will test how much weight I need to use in my BCD in the open-air area of the cenote. She also wants to make sure that I can swim in a way that won’t kick up sediment. The water in the cenotes is predominantly still, which means it takes longer to sediment to re-settle, therefore inhibit visibility for other divers. I feel a bit more at ease when she says she’s going to test my weights and swimming technique. I hope I don’t disappoint. She leads me back to the parking lot and shows me the map of Kukulcan. All cenotes have mapped out routes and she explains exactly what to expect along the route so I am not surprised by anything. She notes that we must exercise more caution to not bump into any formations, which are thousands of years old. We must stay above the guide rope laid on the floor of the cenote and I must always swim behind her, never next to or in front of her. We also have to be more conservative with air consumption. As a recreational diver, I must warn her when I have used up one-third of air, which is significantly less than the warning I had to give in the ocean. I’m not allowed to bring my camera for these two cenotes.