Río Secreto offers a unique eco-tourism adventure exploring an ancient underground river and cave system in Playa del Carmen, Mexico, primarily accessible to those with moderate physical fitness as it involves walking, wading, and swimming through natural formations. All visits are strictly guided to ensure safety and preserve the delicate environment; solo exploration is not permitted. While open year-round, it's advisable to check conditions during the rainy season, though tours typically proceed. The approximate cost for a guided tour usually ranges from $79 to $100+ USD per person, and a typical visit, including preparation and the cave expedition, lasts about 3 to 5 hours. Essential tips include making reservations, wearing swimwear under clothes, utilizing provided lockers, and refraining from regular sunscreen/insect repellent to protect the pristine waters, with professional photography services often available for purchase.