You need to decide how much force you want the waves to generate and how fast you want the robot to move.
The robot's shape, size, and buoyancy will also influence how it interacts with the waves.
How to determine the amount of waves required
Stronger forces and higher speeds generally require longer wavelengths. In addition, a streamlined robot with minimal resistance will require less wave energy than a bulky one.
The density and viscosity of the water will affect how waves propagate and interact with the robot. Denser and more viscous water requires longer wavelengths for efficient propulsion.