You should have said, you saw a guy aboard it, with a scarf tied round his face shouting Ahla Akbar. No seriously, i used to work in a coast guard department of the UK, (fishery protection) and we once, saw a sailboat moving on our radar, we could see the boat visualy, it had it sails down, but was moving, we thought it strange, so (government money didnt cost us anything, and it was something to do) we launched a boat from our ship, Rigid inflatable boat, a fast craft, our guys boarde the boat, they shouted back on the radio, "no one aboard" i was on the bridge of the cutter, with binos, saw a guy in a rubber dingy, rowing for all he could after the boat, turned out to be a frenchman, that had sailed all over the uk, leaving his boat at anchor, and that one time, it got swept by the current, when he arrived back on his boat, we had two of our guys onboard the boat, (but they didnt know how to sail it) and one of our guys towing it. He was glad to get his boat back, didnt even give us a bottle of wine for our trouble.