The NatGeo site says:
A BioBlitz is a 24-hour event in which teams of volunteer scientists, families, students, teachers, and other community members work together to find and identify as many species of plants, animals, microbes, fungi, and other organisms as possible. A BioBlitz gives adults, kids, and teens the opportunity to join biologists in the field and participate in bona fide research expeditions. It's a fun and exciting way to learn about the biological diversity of local parks and to better understand how to protect them.Close to 95 percent of this national park is underwater, so participants can register beforehand to reserve space on a ferry or snorkel boat.
All the details about the BioBlitz appear here, including the FAQ, the registration form for the ferry or snorkel boat (very limited seats!) and educational resources for grades 3-5 and adults.