For an instant Mark was so startled he cried out, and the professor
and the others ran to see what was the matter.

"There-- by the ship! A horrible creature!" exclaimed Mark.

Shouting to Washington to keep the light steady in the direction of
the dock, Mr. Henderson ran toward the moored Mermaid. Jack, Andy,
Bill and Tom, with Mark in the rear followed him.

"Nothing here," said the scientist, after a careful search about. "Are
you sure you saw something, Mark?"

"Positively," replied the lad with a shudder. He described the vision
of the darkness.

"I guess it was a big otter, or maybe an enormous turtle," the
professor said.

CHAPTER V

ATTACKED BY A WHALE

BUT Mark was certain it was nothing like that, though a careful search
failed to reveal anything or any person near the ship. It was too dark
to examine for footprints, and even Mark, after taking a look all
about, felt he might have been deceived by shadows. Still he was a
little nervous, and could hardly sleep for imagining what the thing he
saw could have been.