Andrew laughed and, pulling hard on one oar, swung the dinghy round.
"The buoy's certainly not in the water. We'll try the bank. The tide hadn't ebbed so far when we were here last."
They landed, and plowed through slushy sand. At last Whitney caught his foot in a rope.
"You've struck it after all," he laughed, as he followed up the rope to a ring of large net-corks. "Now, we'll get to work."
Returning to the spot where the rope came out of the sand, he began to dig with a spade they had brought; but he did not make much progress. Water and soft ooze ran back into the hole almost as fast as he could throw them out; his heavy boots sank into the yielding ground; and his oilskins hampered him greatly. When he was hot and breathless, Andrew took the spade.
"The fellow who moored the buoy here, didn't mean it to go adrift," he remarked as he flung the wet sand about.
The spade jarred upon something hard, and Andrew worked its edge under the object while Whitney seized the rope. For a time, they tugged and wrenched at it, and then, when they were gasping and splashed all over, a heavy stone slowly rolled out of its muddy bed. Andrew let it lie and walked back a short distance toward higher ground.
"The next step needs care," he said. "We mustn't move the stone far, because that would show that its position had been changed; but the bank is steep and a few yards will make a difference. If I can shorten the depth by half a fathom, it will satisfy me."
Whitney chuckled.
"That ought to be enough. When your draught's pretty deep it's embarrassing to find half a fathom less water than you expect."