Tonnages (Gross Deadweight)
| Homeward bound | Outward bound | Total | |
| Convoyed | 59,062,200 | 47,491,950 | 106,554,150 |
| Lost | 510,600 | 378,100 | 888,700 |
| Per cent of losses | 0.86 | 0.8 | 0.83 |
Fifteen cargo ships with a deadweight tonnage of 103,692, were lost during 1918 by the Naval Overseas Transportation Service. The removal of the ban of secrecy, vital during the war as a protection to vessels and their crews, discloses that 6 ships, aggregating 42,627 tons, were destroyed by enemy activity, 5 vessels, representing a tonnage of 44,071 tons, were sunk in collisions, and 4 vessels, totalling 16,994 tons, were destroyed by fire and explosion. Seventy-two ships were originally assigned to this service late in 1917, and when the armistice was signed, November 11, 1918, the cargo fleet numbered 453 vessels, including 106 ships ready to be taken over.
Crews of naval cargo ships faced many perils, including the menace of an unseen foe, the danger of collision, and the liability to death by accidents from inflammable cargoes.
Not only were these crews confronted with the normal perils of the sea, says the report, but they faced destruction from torpedo, collision, and other unforeseen accidents that might cause fire in inflammable cargoes. It took brave men to steam week in and week out through submarine and mine infested waters at eight knots an hour in a ship loaded with several thousand tons of depth charges, TNT, or poison gas, not knowing what minute the entire vessel was going to be blown to matchwood.
It is on record that a convoy of fifty ships from New York was disintegrated by a violent storm in mid-Atlantic, and that only two of the number reached France under convoy. "Every ship for herself," the forty-eight others by luck, pluck, and constant vigil, all finally dropped their anchors in the protected harbors of their destination.
The value of a cargo ship is realized when it is known that under existing war conditions each ship cost to operate $100 every hour. Good, bad, and indifferent ships, old or new, fast or slow, were transformed into serviceable craft. The personnel of the Naval Overseas Transportation Service at the time of the armistice included 5,000 officers and 45,000 enlisted men.
The world has been so deeply occupied with figures and facts relating to the havoc by the German submarine that little thought has been centred upon the work of the Allied submersibles. Yet in the way of accounting for war-ships one may fancy that they rivalled the Teutonic craft. Details may be given of the part which British submarines played during the war. This service destroyed 2 battleships, 2 armed cruisers, 2 light cruisers, 7 destroyers, 5 gunboats, 20 submarines, and 5 armed auxiliary vessels. In addition 3 battleships and 1 light cruiser were torpedoed, but reached port badly damaged. One Zeppelin also got back to port badly damaged after having been attacked by a submarine.
Other enemy craft destroyed by British submarines were 14 transports, 6 ammunition and supply ships, 2 store ships, 53 steamships, and 197 sailing ships. In no case was a merchant ship sunk at sight. Care was taken to see that the crews of all vessels got safely away.
In addition to carrying out their attacks on enemy war-craft, the submarines played an important part in convoy work. In the third year of the war one of the British submarine commanders carried out 24 cruises, totalling 22,000 miles, which probably constitutes a record for any submarine. In the first and second years of the war 7 British submarine commanders carried out a total of 120 cruises, extending for 350 days, all of which were actually spent in the enemy theatre.