On the first day of the Gallipoli landings (25 April 1915) at V Beach, Gallipoli, during the landing from SS "River Clyde", Tisdall heard wounded men on the beach calling for help. The men were under heavy machine gun fire from entrenched Turkish forces. He jumped into the water, and pushing a boat in front of him, went to their rescue. He found, however, that he could not manage alone, but managed to enlist the help of first one, and then three more naval personnel. They made five trips from the ship to the shore and were responsible for rescuing several wounded men under heavy and accurate fire, until darkness forced them to stop.