Final answer:
In Washington State, there must be at least two people on board for towed water sports: an operator and an observer.
Step-by-step explanation:
In Washington State, when engaged in towed water sports such as water skiing, it is required by law to have at least two people on board the vessel: the operator and an observer to watch the person being towed and communicate with the operator.
This ensures the safety of the person being towed, allowing for quick response to any situations that may arise. Though specific numbers are not mentioned in the provided material, this regulation is typically enforced by state authorities to maintain safety standards on waterways.
It's part of a broader set of rules intended to protect participants in water sports as well as the natural aquatic environment.