We were told in Mark 3:9 that Jesus asked his disciples to have a small boat ready for him in case the crowd got too large. We can thus assume that he was in this same boat when he was teaching the crowds (Mark 4:1). Presumably, Jesus and all twelve of his disciples were able to fit into this boat. It may have had a sail and it certainly had several oars for rowing. With thirteen people inside it, it might have also been sitting quite low in the water.
A first-century Galilean boat unearthed in 1986 and preserved in the Yigal Allon Centre at Ginosar is 8.2 metres long, 2.35 metres wide, and 1.25 metres deep. If this is typical of boats in use on the Lake of Galilee at that time, a group of thirteen would comfortably fit in it.1
36 And leaving the crowd, they took him with them in the boat, just as he was. And other boats were with him.