The "beach police" (pith helmets and white uniforms) are a private security firm hired by the government to patrol the beach. They are not actual Police Officers in the traditional sense. That is why they are limited in their enforcement capacity. They are there to assist you, so by all means approach one should you have a need or an issue. As mentioned, they can detain (and apprehend) but cannot arrest. They call in the police to do that.
They are there to help you, not to interfere in what they may perceive as a normal tourist activity, which can encompass some very "strange/odd - wide range" of behaviour at times... (grin)
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Do they patrol at night ? I don't Recall seeing them.
Yes they do. You may see them at more at the shows, the busier bars, less walking on foot but more driving in their jeeps to cover more ground as there are less tourists walking at night. Once again - if you need their assistance, they are there to serve. Just ask them!
Negril.com - For the vacation that never ends!
I heard the beach police are called white caps.