Which of the following criteria is under the craft master's discretion?

The criterion of maximum breaker height is indeed within the craft master's discretion because it directly pertains to the operational safety and navigational decisions that the craft master must make while operating in varying sea conditions. This involves assessing wave heights and other environmental factors to determine if the craft can safely transit without risk to personnel or equipment.

The craft master's role requires a thorough understanding of the specific capabilities and limitations of the vessel, which includes evaluating conditions like wave height. Decisions based on this criteria also contribute to the overall safety of the mission and the crew, particularly in dynamic or potentially hazardous environments.

Other criteria listed, such as loss of communications, visibility below 2000 yards, and a fouled LCAC lane, typically involve compliance with established regulations or guidelines and often require a different set of decision-making protocols, where authorities outside the craft master may need to be involved or consulted.