The deep bass hum of an aerial propeller attracted the crew's attention from the catch. Five hundred feet overhead was a coastal airship which had drifted down silently with her engines shut off, and, having just restarted her motors, was manoeuvring into the wind's eye.
Perhaps it was as well that R.A.F. 1164 B carried on her fore-deck a square of canvas painted with the distinctive red, white, and blue circles. This device was a guarantee of her identity as a friend. Without it a small, grey-painted craft might easily be mistaken for a U-boat, with disastrous results.
Then the engines were stopped again. Over the side of the nacelle a leather-helmeted and begoggled head appeared. The pilot, raising a megaphone to his lips, hailed:
"R.A.F. launch ahoy! Any fish to spare us?"
"Right-o!" shouted Derek in reply, but his voice was apparently inaudible to the airship's crew, for the hail was repeated.
"Hold up some fish and let them see," ordered Derek.
One of the men displayed the largest skate, a lozenge-shaped fish measuring more than a yard from fin to fin.
"That's done them!" exclaimed Derek.
But he was mistaken. Like a cormorant swooping down from a beacon, the huge and seemingly ungainly airship tilted her nose and dropped almost vertically until her nacelle was within fifty or sixty feet of the water. Then, with her propeller revolving at a reduced rate, she forged ahead on a similar course to that of the motor-boat.
"By Jove! She's paying out her aerial. That's a smart move," announced Derek. "Easy ahead! Follow her up, coxswain."