If a US Naval vessel were in territorial waters of Ireland the laws of Ireland would be in effect, not those of the FAA. While a majority of the members of this forum are from the USA, there are many from Europe, Canada, and Australia with some from the rest of the world.I replied with FAA/US rules because the OP's question was regarding a naval vessel and I sort of knew the answer from manned flying days. The OP didn't ask for any specific navy, or any specific authority. Had the OP asked specifically about Irish vessels, I would not have even responded.
While most of the basic rules are the same or close to it, many others are vastly different and always quoting FAA regulations has no meaning when outside of the USA.