The Sea Lion was a United States submarine, yet she was not
constructed along the usual naval lines. It was said of her that she
looked more like a pleasure yacht built for under-surface work than
anything else.

It is not the purpose of the writer to enter into a minute description
of the craft. She was provided with a gasoline engine and an electric
motor. She was not very roomy, but her appointments were very handsome
and costly.

There were machines for manufacturing pure air, as is common with all
submarines of her class, and the apparatus for the production of
electricity was modern and efficient. Every compartment could be
closed against every other chamber in case of damage to the shell.

The pumps designed to expel the water taken into the hold for the
purpose of bringing the craft to the bottom were powerful, so that she
seemed to sink and rise as easily as does a bird on the wing. At top
speed she would make about twenty miles an hour.

On a trial trip taken by Ned on the day before the visit of Captain
Moore to the Black Bear clubroom, the double doors and closet which
enabled one to leave or enter the boat while under water had been
thoroughly tested and found to work perfectly.

The diving suits--which had been manufactured to fit Ned and Frank,
Jack and Jimmie--were also found to be in perfect condition.