Ocean Rift originally launched for the Samsung Gear VR, but Welsh developer Llyr ap Cenydd has been experimenting with the use of the HTC Vive's motion controllers to allow for swimming-based locomotion. In the above video, originally posted to Llyr's YouTube Channel, the developer demonstrates how using the motion controllers to simulate swimming motions can move the player's first-person perspective in all directions.
Additional directional control is offered with a small propeller that extends out of the end of one of the motion controllers, and can be toggled on and off. The experiment shows just one novel solution to the issue of locomotion that VR games which don't require the player to remain stationary need to solve.
An earlier demo of Ocean Rift can be downloaded from Llyr's personal homepage. Check out his other prototype for the Oculus Rift, Crashland, too.
