"Beastly dirty job," remarked Vyse, objecting in turn, as he glanced at the oil-smothered water. "All right. Lead on, Macduff!"
Awaiting their opportunity, for Pengelly was kept fairly busy in shouting orders to the men tending the warps and transferring the plunder to the Alerte, the chums made their way under the bridge. Here, secure from observation, unless any of the crew of the quick-firer came aft, they clambered through the gap in the stove-in bulwarks and dropped into the sea.
For the first time they realised the extreme difficulty in swimming in oil-covered water. It was a hard struggle to keep their heads above the surface, and quite a strenuous effort to make progress. To add to the peril, they were liable to be crushed by the hull of the ship as she drifted to lee'ard, while when they reached the wind'ard side they might find that the drift was so considerable that they would be unable to keep pace with it.
"Dog-stroke," gasped Broadmayne. "Better than breast-stroke in this muck. We're all right."
It seemed a fearfully long time swimming under the tanker's squat counter. Then foot by foot they struggled along the Spanish vessel's starboard quarter to where the jagged timbers of the crushed boat still hung from the for'ard falls.
With a gasp of relief the Sub stretched out his hand and grasped the débris. He waited until Vyse had obtained a hand-fast and then cautiously hoisted himself out of the water and gained a temporary refuge by sitting on the edge of the boat's bow-thwart, where his chum soon joined him.
So far so good. They were roughly fifteen feet below the tanker's stanchion-rail. The boat's bows were practically intact as far as the second thwart, and hanging in a vertical position formed a screen from the sight of any one who happened to look over the tanker's side. But their plight was far from enviable. Owing to the swell, the wreckage of the boat was thudding steadily against the tanker's side and turning dizzily as the falls twisted and untwisted. The chums were smothered with black oil from head to foot. Some of the vile stuff had found its way into Rollo's eyes, making them smart exceedingly. Yet in spite of the various discomforts he could not refrain from remarking that they looked like a pair of blackbirds in a cage.
"There's the recall," exclaimed the Sub, as above the hiss of escaping vapour from the Mendez Nunez's steam-pipe came the shrill notes of a whistle.
For a few minutes longer the chums listened intently. They could hear nothing more to indicate that the pirate submarine had parted company with her prize.
"Don't move," cautioned Vyse suddenly. "Look!"