He is close to land.

He has left his earth chest.

But he has yet to get on shore.

In the night he may lie hidden somewhere, but if he be not carried on shore, or if the ship do not touch it, he cannot achieve the land.

In such case he can, if it be in the night, change his form and jump or fly on shore, then, unless he be carried he cannot escape.
And if he be carried, then the customs men may discover what the box contain.