A diving fin system is provided. The fin system includes without limitation a collapsible, leg mounted diving fin. The fin system includes a first section mounted to lower leg and a second section and a third section that can collapse up to and around the lower leg. When collapsed, it can have a very low profile such that it looks like a slightly wider version of the calf area of the leg. It can be also be a three-piece deploying fin, wherein the first section is maintained coupled to the lower leg, the second section slides and rotates to couple to the top of a foot and the third section rotates away from the second section to form the fin blade for use in diving, such as scuba diving.