Convoys reported suspicious lights, and it was believed that these were informers on shore signaling to U-boats. The submarines used various disguises. One, submerged with its periscope showing, lay hidden for hours in the midst of a fishing fleet. Yet the fishermen paid so little attention to it that the French semaphore station, only a few kilometers away, was not notified. A Greek merchantman hove in sight, the U-boat fired a torpedo and the steamship was sunk. The French authorities welcomed our intelligence officers, and together they set about developing an efficient service all along the coast. A U. S. Naval Reserve officer who spoke French fluently was attached to the staff of the French commander-in-chief in Brittany. That coast is rugged and bold, with groups of small islands. The most important is Belle-Ile-en-Mer, twelve kilometers from shore, the first land sighted by convoys going to St. Nazaire, and the last seen on their way home. At the northern end is the famous "Passage de la Tenouse," leading to the bay of Quiberon. Once through this passage and in the bay, ships were considered safe from submarines. One group of our first troop convoys was attacked three miles west of the Point des Poulin, the entrance to this passage, and several shells fired by the transports ricocheted and exploded on the rocky bluffs of the island. West-bound convoys were assembled in Quiberon Bay. Every effort was made to conceal their departure, but the information that enemy submarines seemed to obtain at times was startling. When the merchant convoy system was inaugurated, ships were instructed to anchor off Le Palais, in the lee of Belle Ile. Two days later a submarine laid mines in the roadstead. The next night ships were anchored two miles to the north, but within twelve hours mines were laid there. Lights and signals were not the only means of enemy communication. Some fisherman, seeing the transports in the bay, might go out at night and inform a submarine, which could radio the news to all the U-boats in the vicinity. These were the conditions that had to be met. Every report of suspicious happenings had to be investigated, and the French were quite willing that the American Navy assume this task, as it was responsible for most of the convoy work through these waters. With the greatest care and secrecy, forty-five of the most intelligent fishermen who had boats of their own were selected, and formed into a patrol service. Proceeding with their fishing, they were instructed to watch for any sign of submarines or mines and report it immediately. Furthermore, they were to report any mysterious behavior of fishermen or strangers in boats, and any lights or suspicious happenings along the coast. Experienced detectives were employed, with headquarters at Nantes, to investigate all reports. A flood of them came in from the population who, like the French officers, seemed anxious to aid the Americans.