U-20's crewmen line the deck of their boat.

Without any warning, the U-20 attacks and sinks two medium-sized British merchant ships. In both cases, the ships' occupants manage to escape without loss of life. That evening, the British Admiralty command in Queenstown, Ireland sends a wireless message to all British ships in the vicinity that "submarines (are) active off the south coast of Ireland." Turner receives the message, the first of several such nonspecific warnings.

That evening, as the passengers attend a Seamen's Charities benefit concert in the first class lounge, Turner posts double lookouts, closes watertight doors, and has the lifeboats swung out on their davits so that they can be put into the water more quickly. (The Cunard Line, learning from the 1912 Titanic disaster, has equipped the liner with 48 lifeboats.) The Admiralty neglects to provide armed escorts for the Lusitania, as it had done when the ship last arrived in Liverpool in March. First Lord of the Admiralty Winston Churchill will later explain to the House of Commons that since the Navy didn't have resources to protect more than a few ships, it had resolved to escort none.