Hatches may be vertical or horizontal depending on whether they pierce a bulkhead or a deck. ALL hatches are marked X, Y, or Z (XRAY, YOKE, ZEBRA plus variations).
XRAY -- Provides the least watertight integrity and the greatest ease of access throughout the ship. It is set when the threat to the ship is minimal.
YOKE -- Provides a greater degree of watertight integrity than condition XRAY but to a lesser degree than the maximum condition.
ZEBRA -- Provides the greatest degree of subdivision and watertight integrity to the ship. It is the maximum state of readiness for the ship’s survivability system. Condition ZEBRA is set when the following situations occur:
1. Immediately when General Quarters is sounded.
2. When entering or leaving port in wartime.
3. To localize damage and control fire and flooding when the crew is not at GQ .
4. At any time the CO deems the maximum condition of survivability should be set.
WWG1WGA
Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)