The hydro-glisseur, as its name implies, is a weird sort of craft that skims on the surface of the water and is propelled by a two-bladed aerial propeller. The body consists of six floats lashed together in pairs. Credited with a speed of fifty knots, hydro-glisseurs are used for towing aeroplane targets at high speed, while air-craft hovering overhead try their level best to bomb the targets into fragments.
"You'll want your flying-kit, you fellows," declared Grainger, as the trio prepared for the trial trip. "Unless you want to be as deaf as posts, don't forget your helmets."
Arrayed in leather jackets, flying head-dress and fur-lined gloves—gear that took Derek's thoughts back to those seemingly far-off days at Torringham aerodrome and on the Western Front—the "glisseurs" made their way to the boat-sheds out of which the freak craft were moored.
A few minor adjustments, and the powerful engine fired. Throttled well down, the motor was running at sufficient speed to make the propeller buzz as it cleft the air.
"All ready? Let go!" roared Grainger.
A touch of the controls, and the glisseur gathered way. Soon she began to lift under the enormously powerful drive of the huge propeller, until, with a deafening roar that could be heard for miles, the freak craft quickly worked up to a speed of certainly not less than forty-five knots.
Presently Grainger throttled down.
"There's a Boche submarine alongside Fisherton Quay," he announced. "She came into harbour at lunch-time. I vote we go and have a look at her."
The proposal met with unanimous assent, and a course was shaped for the place where the ex-German submarine was moored.
As the hydro-glisseur approached the quay the speed was greatly reduced. Derek could see the long, unlovely above-water outlines of the U-boat, her deck literally packed with people while from her mast floated the White Ensign over the discredited emblem of the badly-bruised Mailed Fist—the Black Cross of Hunland. For yards either way beyond the submarine the quay was lined with hundreds of interested spectators, for the trophy had been sent for public inspection, a small charge being made, and the proceeds given to local charities.