Mark 3:9

And he spake unto his disciples
In an authoritative way; he ordered and commanded them,

that a small ship should wait on him:
that a boat should be got ready, be near at hand, and attend him, who was on shore; that he might go into it, should there be any occasion for it; and from thence preach to the people:

because of the multitude;
which came from the above parts, and all together made a very numerous body of people:

lest they should throng him;
crowd, press, afflict, and distress, and make him uneasy, that he could not be able to stand conveniently, and preach to them: so that should this be the case, as it was very likely it would, having a small vessel near the shore, he could go into it, and free himself from such an inconvenience.