21 When Jesus had crossed over again in a boat to the other side [i.e., to the northwest shore of the lake, probably in the vicinity of Capernaum], a large crowd gathered around Him along the shore of the lake.
Mark 5:21 Cross References - AUV
Matthew 9:1
1 Then Jesus entered a boat and crossed [back] over [Lake Galilee] and came to His own city [i.e., Capernaum].
Mark 4:1
1 Jesus again began teaching along the shore of the lake [of Galilee]. A huge crowd gathered around Him so that He had to sit in a boat out in the lake [to speak to them], while all the crowd stood on the shore.
Luke 8:40
40 Then as Jesus returned [i.e., to the northwest shore of the lake, probably to the vicinity of Capernaum], a crowd was waiting for Him and welcomed Him.