I attended the AF Police Academy at Lackland.
The Navy used to have Marines serving as Gate Guards and MAs doing internal security.
Shore Patrol is from a ship, any NCO who is on-duty. The SP job is to herd sailors away from the bad parts of towns. When sailors get too drunk the SP carries them back to the ship. And when fights break-out the SP tries to remove the sailors before local LEO shows up.
After the Marines pulled back, then Navy Law Enforcement had to expand. MA is a rate that can be done career long. MAs served mostly at-sea on surface [target] vessels. The Navy developed a 9545 NEC to fill-in the gap for use on Navy bases.
I hold the 9545 NEC.
At most Navy bases the PD is ran by senior MAs. A small Marine cadre forms the training division, MAs for the dog-handlers and crime investigators, while 9545s are patrolmen.
9545s will normally do half a shift standing on a gate, checking IDs and vehicles. Then the other half of the shift in a patrol car. While on patrol they do: money escorts, they respond to reports of larceny, traffic accidents, fights, etc. Together the MAs and the 9545s form the Law Enforcement on Navy Bases.
Navy Law Enforcement personnel routinely work hand-in-hand with Local National [LN] PDs. Few LNs can afford to operate a certified Dog Kennel. So our Dog-Handlers go off-base daily to assist LN PDs with their dogs. We may also provide assistance when LN LEOs need to beef-up their presence during a drug raid.
In some areas the Navy holds a Cooperative Jurisdiction with LN forces. For example in Naples Italy, the US Navy exercises legal jurisdiction over a 500 square-mile area. That area includes 6 NATO bases and a few dozen leased facilities.
Navy Law Enforcement personnel make hourly patrols between all of those facilities in their jurisdictional area. Responding to break-ins, traffic accidents, fights, etc, to protect NATO forces and their families living within that area. I served a 3-year tour in the Naples Italy NATO base PD.
When an Italian LEO arrests you, you WANT a US Navy Law Enforcement personnel to respond to assist in calming down the situation. We do the same for all NATO personnel from all NATO nations. [I have done that]
When a LN hospital takes in a small child from a hit/run traffic accident, discovers that he does not speak the local language. But from the tags in his clothing, he might be an American. You WANT for an American to respond to provide assistance. [I have done that too]
The Navy likes using NCOs on shore-duty as 9545s, because as NCOs it is assumed that they can handle themselves in a more mature manner than 18 year old kids do.
All Navy MAs and 9545s go through the Air Force Police Academy.
The Federal DOL recognizes this career field as being fully Law Enforcement. The DOL has an apprenticeship / Journeyman program that certifies a Police Officer's training and experience at standardized levels. Many US civilian PDs recognize the Federal DOL, some do not.
On the other hand, for 18 year old kids, spending many months, in rotating shift-work, guarding an isolated gate, on the back end of an airfield, I can easily see where it could be considered a very low end job.
You might pull a billet where you walk a circuit between warehouses, checking their doorknobs to make sure they are locked.