Rule of Thirds (189 of 365)

I decided to take a totally different spin on the "Rule of Thirds." Photography isn't the only subject with this rule. Scuba diving, or specifically cavern or cave diving, has one, too. These types of dives are in overhead environments where a diver is unable to immediately reach the surface in the event of emergency. As a result, cave divers developed the "Rule of Thirds": you use 1/3 of your air supply to enter and explore the cave, 1/3 of your air supply to return to the surface, and the remaining 1/3 is available for you or your dive buddy in the event of an emergency.