In summary, the choice between propellers and "wheels" (or specialized traction devices) for underwater robots depends heavily on the intended application and operating environment. Propellers offer versatility and power, while specialized traction systems may be more suitable for specific, surface-hugging tasks.

The main advantage of such systems is that they can provide stable and precise movement over flat or smooth surfaces. However, they're not suitable for deep-sea exploration or navigating rough terrain, which is why propellers remain the dominant propulsion method for deep-sea robots.

These "wheels" are typically magnetic or have suction cups to grip the surface they're moving on, but they're not true wheels that roll on a solid ground. They're more like specialized traction devices adapted for underwater environments.

Now, regarding the use of wheels for underwater robots, it's not entirely unheard of but quite limited in scope. Some underwater vehicles designed for specific tasks, like inspecting pipelines or ship hulls, might use treads or tracks that mimic wheels in a sense.

Additionally, propellers can generate noise and vibrations, which could disturb marine life or interfere with sensitive sonar or acoustic equipment. Designers often have to balance the need for thrust with the requirement for stealth and environmental friendliness.