This instructional scuba video describes the two major types of fins available. There is the paddle fin and the split fin. The paddle fin uses more effort from your leg to push the water. It’s similar to a boat paddle, whereas the split fin is similar to how a propeller from a boat works. The water goes through the blade and creates vortices that push you along. Ultimately the split fin reduces the amount of energy you use, and it saves your air because you’re using less energy resulting in a longer scuba diving or snorkeling adventure.