What are the discrete SUBSAFE boundary groups?

The discrete SUBSAFE boundary groups are crucial components in submarine safety and integrity. The correct choice highlights the significance of ensuring reliable and safe operations under challenging conditions.

Hull structure and sea-connected/seawater systems are essential because the hull must withstand external pressures while maintaining the integrity of internal systems, especially those connected to seawater, which can pose significant risks if not properly managed. The design and condition of the hull structure directly influence the submarine's ability to submerge safely, while the seawater systems, including cooling and ballast, are vital for operational efficiency and environmental safety.

In contrast to the other options, which include elements not typically encompassed by the SUBSAFE concept, the selected answer accurately reflects the key areas of focus for ensuring that critical boundaries are respected to prevent flooding and ensure the vessel's survivability underwater.