An aquatic device is usable in an aquatic environment for a variety of purposes, such as physical therapy, rehabilitation, and/or exercise. The aquatic device permits a person to simulate a walking or running gait cycle in the aquatic environment, reducing the stress/strain associated with walking or running on the ground. An aquatic device includes a foot-receiving member rotationally coupled to a fin member. The fin member, when in an extended position, provides increased resistance as the person attempts to walk or run in the aquatic environment. During a walking or running gait, the fin member moves into a folded position, thus reducing the resistance of the water on the aquatic device. The aquatic device is adaptable and modifiable to have varying shapes, designs, sizes, resistance levels, and/or other aspects.