Contact this Xcaret-based organization to assist with conservation efforts at Playa Xcacel as turtles come ashore to lay their eggs. You can arrange a minimum one-month stay (M$2000) from May to October, which includes three daily meals and rustic lodging in a palapa, but you'll need to bring your own hammock. Volunteering for adults only.

You can also make arrangements to volunteer for one night (voluntary donation M$200) from June to August, which involves patrolling protected nesting grounds from 8pm to 5am.