But the shore people would change their minds about it at sea, on a long voyage.

On such a voyage, with its eternal monotonies, people's intellects deteriorate; the owners of the intellects soon reach a point where they almost seem to prefer childish things to things of a maturer degree.

One is often surprised at the juvenilities which grown people indulge in at sea, and the interest they take in them, and the consuming enjoyment they get out of them.
This is on long voyages only.

The mind gradually becomes inert, dull, blunted; it loses its accustomed interest in intellectual things; nothing but horse-play can rouse it, nothing but wild and foolish grotesqueries can entertain it.

On short voyages it makes no such exposure of itself; it hasn't time to slump down to this sorrowful level.
The short-voyage passenger gets his chief physical exercise out of "horse-billiards"-- shovel-board.