Albert Barnes on Mark 3:9

A small ship. Rather, a boat. There were, properly speaking; no ships on the sea of Tiberias. This was probably a small boat that belonged to his disciples, in which he could sit, off from the shore, and teach the people, without being pressed by them.

Lest they should throng him. They pressed upon him in great numbers. He had healed many; and those who were still diseased pressed or crowded on him, so as to endanger his life. He therefore withdrew from the multitude, and sought a situation where he might be free from danger.

As many as had plagues. As many as had diseases, or maladies of body or mind. The word plague, now confined to the pestilence, does not express the meaning of the original, and tends to mislead.