The tide itself might have told them the direction to take. It was the in-coming tide, and therefore swelling towards the beach.
You may fancy they had nothing to do but follow the waves, keeping the breeze upon their back.
So they fancied, at first starting for the shore; but they were not long in discovering that this guide, apparently so trustworthy, was not to be relied upon; and it was only then they became apprised of the real danger of their situation. Both wind and waves were certainly proceeding landward, and in a direct line; but it was just this direct line the castaways dared not, in fact could not, follow; for they had not gone a hundred fathoms from the point of the submerged peninsula when they found the water rapidly deepening before them; and a few fathoms farther on they stood up to their armpits!
It was evident that, in the direction in which they were proceeding, it continued to grow deeper; and they turned to try another.
After floundering about for a while they found shoal water again, reaching up only to their knees; but, wherever they attempted to follow the course of the waves, they perceived that the shoal trended gradually downward.
This at first caused them surprise, as well as alarm. The former affected them only for an instant. The explanation was sought for, and suggested to the satisfaction of all. The sandspit did not project perpendicularly from the line of the coast, but in a diagonal direction. It was, in fact, a sort of natural breakwater, forming one side of a large cone, or embayment, lying between it and the true beach. This feature had been observed on their first setting foot upon it, though at the time they were so much engrossed with the joyous thought of having escaped from the sea, that it had made no impression upon their memory.
They now remembered the circumstance, though not to their satisfaction, for they saw at once that the guide in which they had been trusting could no longer avail them.
The waves were rolling on over that bay, whose depth they had tried, only to find it unfordable.
This was a new dilemma. To escape from it there appeared but one way. They must keep their course along the combing of the peninsula, if they could. But their ability to do so had now become a question, each instant growing more difficult to answer.
They were no longer certain that they were on the spit; but, whether or not, they could find no shallower water by trying on either side. Each way they went it seemed to deepen; and even if they stood still but for a few moments, as they were compelled to do while hesitating as to their course, the water rose perceptibly upon their limbs.