What altitude must be achieved during a Shamrock reentry from the beach line?

The correct altitude that must be achieved during a Shamrock reentry from the beach line is 1000 feet MSL (Mean Sea Level). This specific altitude is crucial for ensuring safe reentry procedures, as it allows for adequate safety margins and operational effectiveness during the critical phase of descent.

Reaching this altitude is designed to facilitate a stable and controlled reentry, ensuring that all necessary checks and preparations can be properly executed before proceeding to lower altitudes. Operating at 1000 feet MSL during reentry provides enough altitude for pilot decision-making and sufficient time to assess the surrounding environment and potential obstacles, thus enhancing overall safety during this phase of flight.