Unidentified Military Helicopter Encounter

Greetings,
Very recently transited Yucatan Channel northbound back to CONUS lightboat. Was approximately 20 NM northeast of Cozumel when at 1700 CST an unidentified military helicopter approached from the east at an altitude of approximately 100ft. He crossed the stern at about 1/4 mile and took station off the port quarter at a low hover. Hailed him on VHF 16 as “Military Helicopter” to which he replied as “Military Helicopter” in American English with no Latin American accent whatsoever. Asked him if all was okay, as no one had hailed us prior to his arrival. He didn’t say, he then asked simply and directly for our official number, hailing port, last port of call and our registered tonnage, which was immediately passed back to him. He then very curtly said “Have a safe voyage”, and cleared out to the northwest still at a low altitude till he was over the horizon, was able to follow him for a little on the 10cm radar. While he was clearing to the northwest, could hear him in a one-sided conversation over VHF 16 apparently to his tactical air controller or whoever his controlling authority was. He was reporting us and two others as “VID surface track’s” and he used four digit 4000 series surface track numbers like USN NTDS systems (e.g., track #4121) and reported our courses/speeds, names, track numbers and the info that he interrogated from us. Could not hear the other side of that conversation, so don’t know if he was still going out on VHF 16 accidentally or if he was on some sort of trunked system.
The aircraft WAS an SH-3 Sea King helicopter, but was NOT wearing a U.S. Navy or Coast Guard paint scheme or aircraft roundel. His paint scheme was a much darker grey and black than USN uses as well I believe I saw a very small red/black/green roundel on the starboard side of his airframe as he passed astern, once he took station off the port quarter he had the sun behind him and it was much more difficult to see in detail. I am certain this guy or at least the guy on the radio was either American or US government as I know a another American on the radio when I hear one as well when he was passing our info back he was using the USN verbal lexicon of “tack” instead of “dash”, just like a good USN/USCG would. Obviously I am well aware of the USN/USCG/LE counter-narcotics presence and operations in the area.
Was curious if any others have had a similar experience in the area or know who the guy belongs to. He was in no way harrassing and was very professional and curt. Was just trying to figure it out as an online search does not show SH-3’s as part of either the Mexican Navy or Air Force’s inventories. Possibly USN/ICE loaner to Mexico?

Look like this? :

Same airframe albeit with a FLIR ball on the nose and a dark grey and black camo paint scheme.

DEA

http://www.deamuseum.org/als/air.html