Every autumn, mother sea turtles visit Cancun's beaches to lay their eggs in the sand. The eggs hatch and each baby turtle flips and flops its way down the beach and scrambles into the water, where he or she is swept into the safety of the ocean. In theory...
To assist these adorable little creatures, many resorts in the Hotel Zone (including the Royal Sands & the Moon Palace Resort) collect turtles on the beaches at night (if you see flashlights or vehicles on the beach at night that could be why) & allow their guests to release them in the evenings. [Jen blogged about this here.]