We anchored about 100 miles out of Gibrlater on the Spanish Coast. About dusk, a jeep, with radar on top, and towing a trailer with two off road cycles pulled onto the beach, and behind some old ruins so just the radar was showing. We went ashore to talk to the "Marines". They were watching for smugglers. The next day, we saw both the smugglers and revenuers in Gibralter. Both sides had Fountain or Cigarette boats, with two 750 hp I/Os and and three 300 hp outboards mounted on the transoms. There was also a ramp, for a Zodiac to be launched over the motors and pulled up on the deck. All mat grey paint. The only way you could tell the good guys, was a small emblem. We saw some similar Spanish boats up the coast by the Portguese boarder later in our voyages.
They left the docks about the same time, and sped off into the night. The cat and mouse game went on every night. Of course the smugglers could not be arrested in Gibralter, because the contraband went from Africa (Morocco) to Spain. The British go fasts were captured smugglers boats.
The same thing happens off our coasts. When going from Dry Tortugas, to Key West, at night, I picked up a radar target, which "hid" behind a nav aid. As we passed, this black boat running dark shadowed us for about half a mile, and then the boat which was sailing with us, about a mile behind. Then they sped off into the night. These were our DEA guys. We saw them leaving Key West the next night. They run every night out of the keys--and look for suspicious boats. Very fast, and stealth.